Only drink bottled water. All the tap water in India is contaminated with pollutants and amoebas. By only drinking good bottled mineral water you will help avoid getting sick. The only brands I recommend are Bisleri, Kinley & Aquafina. Other brands are not trustworthy.
Stay well hydrated. India is typically hot and dry. Drink at least 2 liters (1/2 gallon) per day to stay healthy and strong.
If you’re trekking, bring a water filter. In rare cases where bottled water isn’t available such as while trekking, you’ll need a Katadyn Pocket Water Filter or at least a LifeStraw so that you can get safe water from flowing rivers. Boil it as well if possible and you can also use Iodine tablets to be extra safe.
Coconut water is amazing. Fresh coconuts are extremely good at hydrating you, boosting your electrolytes and making an upset stomach, happy. Although, don’t drink coconuts unless you’re satisfied with cleanliness of both the straw and knife that the vendor is using.
Chai is great in the early morning. Chai is good for digestion because it has ginger and cardamom added. It should be safe to drink as long as you see them boiling it and you’re certain the cup is clean. Price should be no more than 10 rupees.
Coca-Cola can be a godsend. There’s a popular folklore that Coke kills bacteria and aids a disturbed stomach. This may or may not be true but it sure is nice to have a cold Coke on a hot afternoon in India!
Electrolytes are a must. If you get dysentery, electrolytes are a must for staying hydrated. I recommend bringing one box from home because otherwise they can be low quality and taste a bit nasty if bought in India.
Avoid ice in drinks. Since the ice is most likely created from a poor quality water source I advise you to not have any drinks with ice in it. If the drink such as Coke has been chilled in the fridge, that is of course fine.
Don’t brush your teeth with tap water. As annoying as it may seem, I advise you to only brush your teeth with bottled water. This is because your gums can be a direct path to the blood stream and therefore easier for infection to get in.
Shower with care. Don’t open your mouth or eyes in the shower to help avoid the water getting in any unwanted orifice.
Bathe in holy rivers at your own risk. Taking a dip in the Ganges can be a magical experience but again, close your eyes and mouth and block your nose and ears to avoid getting too much water in the wrong hole.