The loser writes, directs, and stars in a 30-second commercial for a fake product the league invents, usually something that mocks their season, like a draft-guide-shaped paperweight. Full commercial sincerity, jingle included. Aired at the draft party on a loop.
Budget note: this one costs nothing but dignity, which makes it a strong pick for leagues that would rather spend the pot on the champion than on the loser's downfall.
Seen in the wild: fantasypunishments.com