Can you drown by drinking too much water?

Extremely unlikely. A normal healthy person cannot drown by drinking too much water except in an extremely rare situation. He would have to drink a lot of water, perhaps 1-2 gallons. His blood sodium would be diluted too much, leading to brain swelling and/or seizures (some of the ways water intoxication kills people). In his semi-conscious state, he vomits water from his stomach, sucks it into his lungs, and drowns.
No. Calculate your body weight in pounds your daily requirement is half your body weight in ounces. If you happen to drink coffee them multiply x 3 the ounce of coffee add that to above requirement.
No. Drowning occurs when water enters the lungs and is not related to how much you drink. Drinking too much water can however, result in other problems.