i use a scepter 5 gallon jerry can, and a 2 gallon RinseKit Plus for pressurized water storage/cleaning duties. I like the fact that I can remove the RinseKit from the truck at any time, and I keep all my soaps, sponge, scrubbies, and a lightweight towel in it for cleanups/showering... I haeat up a gallon of water on the stove, and pour 1 gallon of cold water int he rinsekit, add the hot water, and then pressurize the system with the booster pump (bicycle pump). rinse off, soap up with camp soap (low sudsing soap, bio-degradable) and then rinse off.. I typically use less than 1 gallon to shower. I do plan to get a tank like this...
https://www.frontrunneroutfitters.com/en/us/front-runner-upright-water-tank-with-two-cut-outs-flat.html but preferably shorter... this one is too tall... I like that it is thin, can be left mounted in the truck, and have the nozzle setup so i can put a valve and quick connect at the rear of the bed, and make it a gravity feed for the rinsekit, or for a quick washup if I need it. I bring water bottles for drinking water, but I do treat my water storage containers before and after every trip with a cap of chlorine & water... and multiple rinses.