There seems to be an interest in staying clean in an emergency situation.
That said, I have selected 3 YouTube videos for food for thought. :-D
The first one is a Yuppie outdoor shower. Not for emergency situations unless you have a generator. But heck, there is preparedness and then everyday enjoyment!
Here is a Camp Shower, 1 gallon jug plus black plastic shower stall. This is survival or camping. Lots of good info.
Solar shower style that I eventually bought, used in an emergency situation in your own shower. :)