DM's Guild has an offering called Tavern Games. It has some rules for gambling in general, plus billiards and darts. In other words, typical bar games.
I suspect that you're just looking to briefly describe what game they're playing, and not looking for actual rules. Just think of the sort of games folks play in bars these days. I'd probably rule out trivia contests; that's too modern.
Checkers. Chess. Go, or any other sort of traditional board-and-pebble game. Marbles would require a clear floor space.
I remember pitching pennies toward a wall in high school (Who, me skip class?), kind of a small scale version of horseshoes.
Outdoors type games would include horseshoes and variations on lawn bowling.
Perhaps arm-wrestling?