Someone who only drinks alcohol when with acquaintances who are drinking.

A large British moth (Euthrix potatoria).

plural of drinker moth

Alternative form of nondrinker (“one who does not drink any specified beverage, especially alcohol”)

Someone who drinks water, especially in preference to alcoholic drinks; a teetotaler.

plural of two-fisted drinker

(figuratively, idiomatic) Someone who can handle their liquor well / A person clutching a drink in each hand.