Chug a pint (or quart) of milk, run a quarter-mile lap, and repeat until a full mile and a half-gallon-plus of dairy are done. Very few finishers keep it all down, which is why the rules specify an outdoor track. One camera on the runner, one on the milk.
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.