I usually just bring a small bottle of doc bronners, or similar castile soap. I use it to wash my dishes, or myself when I get too dirty and sometimes my clothes. I hear you can brush your teeth with it too, but it really doesn't taste good so I never have yet. If theres no soap, then I'll scrub it with some dirt, or sand and then rinse.
it seems strange saying that I clean stuff with dirt...it works though, at least it makes it look clean which is good enough for me!