Safe Drinking Water in India
NO to tap water in India at any cost.
Yes, it is a WARNING and must be taken seriously. Water of course is the number 1 cause of stomach infection in India.
For safe drinking water in India, bottled water is the only option I recommend.
Though every third shop in India sells bottled water, generally called by the name Mineral water and is mostly sold under the brand names of Bisleri, Kineley and Aquafina, but buying from a reputed shop is the best option. By reputed shop I mean the one that appeals visually from the perspective of cleanliness at least.
Cost of bottled water may wary from the size of the bottle and of course from where you buy.
Secondly, for cold water, I would prefer freezer cold rather than having ice for obvious reason.
Now in case bottled water is not available but you have to stay hydrated, I recommend 1) carrying Iodine Tablets with you and 2) boil water if you can.
Other option for filtering water is to keep pocket water filter with you. Katadyn Pocket Water Filter and LifeStraw Personal Water filter are 2 excellent products which you may buy depending on your budget.