There are a lot of people that have some very nice fancy outdoor showers going, and I'd like to step it up to one of those someday, but right now, like nearly everyone else, money is a little tight and that isn't where I choose to spend it. Here is my solution:
Here are the complex instructions to make your own!
1. Get a cat, get litter for said cat.
2. When bucket that litter comes in is empty, clean out and fill with water.
3. Set in the sun and wait for it to warm up.
All kidding aside, it really is fun to take showers/bathe outdoors in the garden, and if you don't have the money or the plumbing know-how to build a "for-real" outdoor shower, this is nearly as good and costs nothing.
Or for about $15 you could buy a camping shower and then build a catchment device or you could even just repurpose a well cleaned out concrete mixing tray you have laying around for a water-catching floor?
I'm going to start thinking of plans for a $10 or less nice outdoor shower, though it probably won't happen until next spring.