Have some basic rules for your personal health:
Care in what you eat and drink is the most important health rule: stomach upsets are the most likely travel health problem.
If you don't know for certain that the water is safe, don't drink the water and that includes ice. Reputable brands of bottled water or soft drinks are generally fine. Boiled milk is fine if it is kept hygienically. Tea and coffee should also fine, since the water should have been boiled.
The food slogan:
"If you can cook it, boil it or peel it you can eat it. Otherwise forget it."
Salads and fruit should be washed with boiled water or peeled where possible. Don't become paranoid, trying the local food is part ot the experience of travel, after all.