just a comment from hurricane lessons learned... a dedicated (no pesticides) pump up garden sprayer painted black provides pressure for a quick rinse shower.... some videos availaable on those equipped with a smaller hand shower head....

a 75' length of 3/4" hose will hold about 2 1/2 gallons of water, and in bright Florida July sun reached 165F in one hour... as hikermore commented small amounts to handle safely

a 2mil contractor bag filled with 2 1/2gal of water, laid flat in a sunny surface with air removed from bag so that the bag touched the top surface of the water... open end held up by a 2x4 and second placed on top to seal from wind will also near the 165F number in one hour... this is very dangerous to handle... be prepared to dip out the water with a sauce pan

I have multiple propane camping stoves, but the one I really like for quick heat is a Gas One asian style flat single burner that can use butane cylinders or has an adapter hose for 1# propane (that I use)