School swimwear
When I was at school, we had mixed swimming lessons. The boys wore trunks and the girls wore 1-piece suits. If someone forgot their kit, the rule was as follows:
If they forgot once, they were given a spare pair of trunks/costume.
If they forgot a second time, they had to swim naked.
If they forgot a third time, they had to swim naked and then spend the rest of the day naked.
If they forgot a fourth time, they had to swim naked and then spend the rest of the week naked.
If they forgot a fifth time, they had to spend the rest of the school year naked.