I have some Jockey underwear that is some kind of a hybrid brief--longer leg than a normal brief. They look a bit like cycling shorts, but shorter in the leg. They are all synthetic, which means they dry in a about an hour after I wash them. I take two pair--so I can wash one each day, and wear clean undies all trip long.

And they are black, so they can also double as swimming trunks if I need them...