On the league's next group trip, the loser plays flight attendant: with crew permission they hand out snacks, collect trash, and endure an intercom announcement explaining their situation to the whole plane. Requires a friendly crew, which Southwest has famously provided. Passenger applause determines whether they 'earn their wings'.
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.