Wear your panties for an entire week, but with some extra rules to make it more interesting:
- During that week you are only allowed to use 4 pairs of panties
- You are not allowed to wash them
- You can use the toilet three times a day. If you need to use it more, pee through the panties.
You are allowed to switch them after peeing through a pair, but since you can only use four pairs they will eventually all start smelling a bit if you can't control your bladder.