Another consideration is electrolytes. If you sweat and drink a lot of water, you are diluting the electrolytes in your system, especially sodium and potassium. Seriously consider making one or some of your waterbottles one of a sports drink. There have been fatalities from too much water, not enough electrolyte.
I have found that sports drinks vary a lot in both quality and how any given individual reacts to them. I have had the best luck with a drink I have used for 40 years, Vitalyte. (It has changed names several times but not the formulation. Started as Gookinaid/ERG.) It is cheap, about $18 for a can that will mix up ~40 waterbottles. It does contain glucose so you may have to take that into consideration with regard to your diabetes. REI carries it.
Ben