I don't - it's extra weight, and typically if I'm exerting myself it's better to wash all over than
worry about making myself smell like the manly smell of "Glacier" "Ocean Breeze" "Action" or just
plain old "Old Spice", as opposed to "Funky hiker man" <img src="/forums/images/graemlins/smile.gif" alt="" />

You wanna practice what'll work anywhere? take 3 cups of lukewarm water in a bowl and a very tiny tiny tiny bit of soap or campsuds with a polyester liner sock - step into your bathtub and give yourself a sponge bath with the sock. Do the same in the boonies, with dry clothing to hop into
when you are done. You'll be amazed how much cleaner you can be/feel with only about 3 cups of water - which can be warmed up by a camping stove. Trick is to use very little soap. Seek privacy if that's your preference or to save others from poking out their mind's eye from seeing you. (I'm a 275 lb big hairy dude, so I know what category I fit in!)