Seven days of exclusively cold showers, verified by a thermostat photo or a very honest household witness. No gym-sauna loopholes. The punishment that follows the loser into the most private minutes of their day.
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: fantasyleaguelottery.com