Drinking an alcoholic beverage, usually beer, at the same time with two or more people at the beginning of a social party/drinking game. Commonly used at the start of flippy cup, drinking a shot with others, etc.
Ready, Set, Go. Clink Sink Drink. (beginning of flippy cup)
When drinking a combination shot, such as an Irish Car Bomb, or vegas bomb, where there is a small shot glass full of booze, and a pint glass half full of beer or red bull; the entire shot is consumed by dropping the small shot glass into the half full pint glass, typically preceded by a cheers. Thus Clink: raise and tap shot glasses, Sink: Drop shot glasses into pint glass, and Drink: Consume the entire beverage.
Referring to one's scale of drunkenness, this is the point in the night when, unless you choose to drink more, you're drunkenness level will surely begin to sink.
Kelly took one look at her flask and knew the choice came down to one simplefact: drink it or sink it.