Spit Showers; I know a guy that can take an entire shower with 1 liter of h20. He strips, squats,fills mouth w/ water, squirts needed areas(pits and crotch), adds a little soap, fills mouth squirts water. He then does the same for the crotch of his shorts. He swears by it.
I myself heat a small amt of water, lather areas(clothes or body, just key areas), rinse with little wet towel or water. The key is NOT to use a lot of soap. Don't lather arms, legs torso, just key areas. I use small wicking towels to dryoff. This is very refreshing but i don't do it every night.