I use a mesh bag and store it in the camper tub, b/c we shower at the bath house. This summer I hit the thrift store and bought a few things that I just tossed after I was done wearing them. This came in handy with the youngest ds who gets filthy. I take old ratty clothes for him that are almost too small. That way when he wrecks them, I trash them. They are too wrecked to send to goodwill and too dirty to even worry with washing when we get home.
We ended up with a bunch of wet stuff returning home this year, b/c it rained bad. We tossed it in the back of the truck and I washed it soon as we got home.