The loser sings the national anthem, unaccompanied, before a local minor-league or little-league game. Vocal talent is not a prerequisite, which is the point. One Reddit league got their loser a AAA baseball anthem slot and called it the funniest thing they'd ever seen.
Heavy sentence
Severity 4 punishments are the ones people talk about for years, which is exactly why they need full league buy-in before week one. Put it in the constitution, set the deadline, and agree on proof requirements up front.
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.