I combined information from all three companies. The six main claims made about alkaline water and my response to each claim include:

As part of a review of evidence that is alleged to support health claims of alkaline water, I examined the "Kangen Water Proof Book" (p 46-56).  I noticed a paper titled, Citrate therapy for polycystic kidney disease in rats. The study was published by George A. Tanner and Judith A. Tanner  in Kidney International, Vol. 58 (2000), pp. 1859–1869.  Since the paper actually had nothing to do with alkaline water, I was curious why Kangen (or whoever produced the document) reproduced the paper in its entirety (pp 46 - 56) and highlighted sections that allegedly supported the benefits of alkaline water.  I wrote to Dr. Tanner (to ask him if he had authorized the use of his paper to support alkaline water claims.  He replied with the following comments.  (reproduced with permission) Dear Randy, Thank you for the information. I was not aware that Kangen representatives were citing my Kidney International paper to support claims for a beneficial effect of electrolyzed, alkaline water. A simple calculation shows that if the pH of water is increased even to an alkaline pH of 10.5, the amount of base (OH-) present is, physiologically speaking, inconsequential. A pH of 10.5 corresponds to an OH- concentration of 10-3.5 moles/liter or 0.3 mEq/liter. The typical acid burden on an average American diet (meat + vegetables) for an adult is about 70 mEq/day. Thus, drinking a liter of electrolyzed, alkalinized water would buffer less than 0.5% of the acid formed by metabolism of foodstuffs and would have an undetectable effect on acid-base status. Based on my studies in rats, studies of others in experimental animal models, and recent controlled clinical trials (de Brito-Ashurst et al. J Am Soc Nephrol 2009;20:2075–2084 and Phisitkul et al. Kidney Int 2010;77:617–623), there does indeed appear to be a beneficial effect of alkalinizing salts (e.g. sodium or potassium citrate or bicarbonate) in animals and people with various forms of chronic renal disease. The alkali doses administered in these studies are very much larger than can be obtained from electrolyzed water and do have an impact on acid-base balance. Although I have not researched the topic (as you have done), I am very skeptical of any claims for a beneficial health effect of electrolyzed, alkaline water. My Kidney International study does not support the health claims of the proponents of this treatment. Sincerely, George Tanner, Ph.D. Professor Emeritus Department of Cellular & Integrative Physiology Indiana University School of Medicine

1. Ionized Water Balances body pH because it is very alkaline - "Maintaining an alkaline pH (6.9-7.2) helps us to maintain an environment in our bodies that is NOT conducive to disease. It may take years depending on how acidic your body is, but Ionized Water, because of its alkaline properties, will flush acid waste from our bodies."
   
   Most alkaline water representatives don't like to admit this, but the alkalinity in their ionized water is due to the Sodium Hydroxide (NaOH) formed during electrolysis if salt is the electrolyte in the water.  When this Sodium Hydroxide enters the stomach it is immediately neutralized by the strong stomach acidity back into water and salt ions.
   HCl + NaOH → Na⁺  Cl^- + H2O
   
   > There is no reason to expect that the water formed when the alkaline hydroxide ion is neutralized will retain any special characteristics (even if it had some to begin with) or that salt which results from the neutralization process will have any special properties.
   
   > The alkalinity level of the incoming water relative to the acidity of the stomach acid and to the pH of your body's well-buffered blood are negligible. This means that there would be almost no resulting effect on pH of the body.  I found this article which does a good job of describing the chemical and biological impact of alkaline water in the body.  The article concludes, "For this reason, the pH of the water you drink is completely and utterly meaningless. It has hardly any physico-chemical meaning, and it certainly has zero practical significance."
   
   > Notice the statement "It may take years depending on how acidic your body is, but Ionized Water, because of its alkaline properties, will flush acid waste from our bodies.". There are two problems here: since "It may take years" for the product to work and since there is no way to measure the claim that alkaline water "will flush acid waste from our bodies.", there is no way an individual can determine the truth of the claim.
   
   > When the facts above are mentioned to counter alkaline water claims, this next argument is deployed, "By looking at the pH value of the stomach alone, it seems that alkaline water never reaches the body. But when you look at the whole body, there is a net gain of alkalinity {bicarbonate, HCO3 ¯, created when HCl is made} as we drink alkaline water. Our body cells are slightly alkaline. In order for them to produce acid, they must also produce alkaline, and vice versa; just as a water ionizer cannot produce alkaline water without producing acid water, since tap water is almost neutral."
   
   This sounds reasonable until you realize first that a healthy body is perfectly capable of adjusting to pH changes that occur in response to both normal diet and metabolic processes - if that were not the case, eating would trigger severe alkalosis, and a little exercise might cause fatal acidosis.  If a person’s body is not able to maintain normal pH levels in response to diet and metabolic processes they should see a physician as soon as possible and not look to alkaline water for a cure. 
   
   Second, and more pertinent to this discussion, simply taking a few extra breaths (hyperventilating) is enough to raise the pH of your blood (by increasing the bicarbonate level) - you don't need a $1,000 to $4,000 machine.  As soon as you stop hyperventilating, however, your blood pH levels return to normal - the same thing would happen if any pH change were actually caused by drinking alkaline water.
   http://georgiahealth.edu/itss/edtoolbox/GeorgiaLabs/AcidBase/hyper_hypoventilate/HyperHypoventilation.html
   http://www.unf.edu/~mhough/page4.htm
   http://www.chemistry.wustl.edu/~edudev/LabTutorials/Buffer/Buffer.html
   
   The pH of fluids in the body's cells is not altered by a normal diet that contains acidic as well as alkaline foods or drinks.  Any alkaline substance that enters the stomach will be immediately neutralized by the acid environment.  As the stomach contents pass into the small intestine the acidity is neutralized by sodium bicarbonate from the pancreas.  The stomach must be acidic to kill microbes and to initiate the process of protein digestion.
    
2. Redox potential, not pH, is the crucial factor – So now it's not really pH at all but the redox potential of alkaline water that's important.  The claim is made that, "...when you divide tap water with electrolysis you can see the ORP fluctuate by as much as +- 1,000 mV.  By electrolysis we can obtain reduced water with negative potential that is good for the body.  When taken internally, the reduced Ionized Water with its redox potential of -250 to -350 mV readily donates its electrons to oddball oxygen radicals and blocks the interaction of the active oxygen with normal molecules." Since the only measurable biochemical action of alkaline water is a possible insignificant and transitory rise in blood pH due to the bicarbonate ion, and none of the original OH¯ ions ever make it into the body except as ordinary water molecules, all of the additional discussion about the redox potential, reduced water and ORP is nothing but misdirection - smoke and mirrors.  A lot authoritative sounding chemical lingo is thrown out that is completely meaningless and unintelligible to the ordinary consumer. Compare these descriptions to chaff dumped out of an airplane to confuse the consumer enemy. "aircraft or other targets spread a cloud of small, thin pieces of aluminium, metallised glass fibre or plastic, which either appears as a cluster of secondary targets on radar screens or swamps the screen with multiple returns. Opposing defenses would find it almost impossible to pick out the "real" aircraft from the echoes from the chaff." 
    
3. Ionized Water is a powerful antioxidant - "Since Ionized Water is a liquid antioxidant, it is easily absorbed into the body which makes it much more effective and powerful antioxidant. Once the Ionized Antioxidant in the form of Hydroxyl Ions (oxygen molecule with an extra electron) donates its extra electrons to free radicals (oxygen molecule that is missing one electron) you are left with lots of oxygen. Ionized Water gives you Energy by providing your body with lots of oxygen!"
   "Claims that "ionized" waters are antioxidants are untrue; hypochlorites (present in most such waters) are in fact oxidizing agents." (Stephen Lower, chemist)
    
4. Colloidal Hydrogen - "Research focused on dissolved hydrogen released through electrolysis of water was presented at The Japan Functional Water Association Meeting in late December of 2002. It reported that Kangen water^(TM) is effective in controlling the oxidation of lipids in the body. It also reported that dissolved hydrogen present in the colloidal state has a higher activity level than active hydrogen produced at the instance of reaction."
   
   There is absolutely no evidence in reputable scientific or medical journals to support the claim that the relatively minute quantities of hydrogen gas dissolved in drinking water has (or can have) any biological activity in the body.
    
5. Cluster Size - "Approximately 15 years ago, with the help of nuclear magnetic resonance (NMR) 1 appliance, it was confirmed that water does not exist in single unit molecules, but forms a molecular population (cluster) 2 out of approximately 13 water molecules. These clusters are constantly repeating an aggregation-disaggregation process. The quality of water depends on the size of its clusters. For example, small clusters have active molecules that increase the capacity of water to dissolve elements (solubility), let elements pass through (permeability), and let heat pass through (conduction). Electrolysis causes the water clusters to break, and Kangen water^(TM) has clusters made up of five to six water molecules resulting in a lower molecular weight. This is approximately half of that of tap water (12-15 water molecules/cluster) and is most beneficial for your health."
   
   The alleged formation of smaller clusters is often used to explain some properties of alkaline water.  There is absolutely no evidence in reputable scientific or medical journals to support the claim that liquid water can be stabilized into any fixed-size cluster.  Even if it were possible to demonstrate the formation of stable water clusters which would survive the environment of the stomach and the small intestine where water absorption occurs, that would not explain how clusters could possibly be beneficial to health.  Water enters cells as individual molecules, not as clusters, so the obvious conclusion would be that the formation of stable water clusters (if they existed) would actually inhibit water absorption not promote it.  For some background on where this notion came from and a critique of the NMR supporting 'evidence' you can read this article by Paul Shin, Ph.D., an authority on NMR technology.  Dr. Shin concludes his article with "There is no “solid” data to support the proposed hexagonal structure for water in the liquid state. In this book Dr. Jhon simply does not provide convincing evidence to support the miraculous properties of Hexagonal Water. Since all “hexagonal” or “clustered” water claims that can be found have the same dubious basis, the whole concept of hexagonal water is filled with too many holes to “hold water” for me." 
   
   One of the more ridiculous claims I have seen stated, "The main cancer prevention capacity of alkaline water is found in the property that its molecules stay in smaller clusters than the molecules of ordinary water. Since they’re smaller, these molecules can actually reach finer spaces in the body which normal water molecules cannot reach." First, as soon as the alkalinity is neutralized in the stomach, there is no reason to expect that the resulting water molecules would retain any "alkaline" properties like smaller clusters (if smaller clusters formed - which they don't).  This quote also demonstrates a complete ignorance about chemistry, physiology and biology - there is no evidence that water molecules in the blood, plasma or cells form stable clusters that have some magical properties.  There is, of course, the minor problem, that alleged stable clusters in the original alkaline water would need to disassemble so they could be absorbed as individual H₂O molecules, reassemble as stable clusters in the blood, disassemble again into individual H₂O molecules for transport into cells, reassemble into stable clusters, and then actually do something to prevent cancer - none of these claims has ever been demonstrated.  Finally, the idea that smaller clusters can somehow "reach finer spaces in the body which normal water molecules cannot reach" is absurd since the hypothetical clusters would be larger than individual water molecules and the body does not have a bunch of "finer spaces" that are inaccessible to water molecules.
    
6. Healing Properties - "The only aspects of Kangen water^(TM) we are allowed to speak of or write about are abnormal gastrointestinal fermentation, chronic diarrhea, indigestion, hyperacidity, and the astringent effect. Although these are the bases of more significant illnesses, speaking of them is against the law. There are numerous cases in clinical studies conducted by doctors or pharmacists that found drinking Kangen water^(TM) cures various illnesses. It is also known that driving out active oxygen from the body with Kangen water^(TM) inevitably boosts the natural healing power."
   
   The only Healing Property Descriptions the alkaline water companies are allowed to get away with, because of Federal Drug Administration and Federal Trade Commission rules against fraudulent advertizing, are the vague, non-specific, generalized claims that do not require proof - as long as they include a disclaimer that the product does not treat specific diseases.  In order to make a claim that a product actually "cures various illnesses" the claim must be proved by reputable, reviewed clinical studies.  Promoters of these products have not demonstrated any such proof despite such meaningless statement as "There are numerous cases in clinical studies conducted by doctors or pharmacists that found drinking Kangen water cures various illnesses."  If alkaline water were actually able to cure any disease, these companies could provide the evidence to win FDA approval and sell the product as a legitimate medical device (or product).  The primary way companies get around the FDA and FTC rules against marketing untested products as cures for diseases is to use testimonials in which a satisfied consumer documents how the product has cured a specific disease.  I analyze and these claims and clinical studies here.