Alkalinity of the water while fasting in my opinion is not an issue, in general, if the minerals are balanced. I suspected ppl who had negative experience with it while fasting, had a problem with the mineral imbalance in the alkaline water, which was man-made. I.e. probably few minerals are used and not in very sensible proportions. Unfortunately lab tests are needed to track the mineral content and with so many options and companies making it it is neither standardized nor reliable to even have the tests done, since content may vary depending on the machine settings or the life of the filters/minerals in the cartridge used.