noun
drinking buddy
Colloquial term for a friend you regularly drink with; casual and friendly.
週末はいつもの飲み友と居酒屋に行く。
On weekends I go to an izakaya with my usual drinking buddy.
彼は大学時代からの飲み友だ。
He's been my drinking buddy since college.
飲み仲間 is a slightly more formal or group-oriented term for drinking companions, while 飲み友 feels more personal and casual.
Compound of 飲み (drinking) and 友 (friend). A straightforward modern colloquial coinage.