The loser watches a complete franchise the league selects, all five Twilight films is the documented standard, then delivers a live five-minute defense of a position the league assigns (Team Edward or Team Jacob) on a public stream, taking questions. Preparation is verifiable; enthusiasm is mandatory.
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.