This was linked in the other question about alkaline water that I already linked:
Since the "paper" in question does not make it clear what method alkaline water could have any effect at all makes it difficult to debunk a specific claim, since none was really made. This is the first flaw: Since the claim made no mention of a possible way in which alkaline water can have any curative effect, even if all the data they presented was accurate and correct, the best claim that could be made is only a correlation. They have established no causation.
Despite this lack of a mechanism, there is mention in the introduction about free radicals and other oxidative stress playing a part in the development of diabetes (which type is not described). Since alkaline water does not significantly effect the pH of the body - and definitely not by the time it reachees the intestine where the water can be absorbed, then the alkalinity of the water can have no protective effect against oxidative damage.
In addition to this, drinking alkaline water after diabetes has already been developed will do nothing to restore oxidative damage to the tissues that has already been sustained (I guess much like trying to splint a bone that has already set badly). In this case, their introduction giving a plausible-sounding problem does not match with their proposed therapy.
As zefciu pointed out, type I diabetes is caused by an auto-immune reaction while type II is caused by insulin resistence of the cells that take up insulin.
In the case of type I diabetes, the alkaline water would need to prevent the immune system from attacking its own beta cells (the ones in the pancreas that produce insulin), allowing the body to regenerate them. This would indeed be miraculous.
In the case of type II diabetes, the water would need to restore the cells ability to take up insulin or at least improve the uptake of insulin. Since no active ingredient would make it in to the body and the pH is unaffected by drinking alkaline water, there is no possible cause of this insulin sensitivity to be improved.