A tablecloth, bedsheet, shower curtain, large beach towel, pretty fabric as a toga, state flag, etc...saw pics from a social that had the same theme and somebody wore a Twister mat! It was really cute!
Bubble wrap, duct tape (over a tube top or as accessories), painter's overalls, smocks or aprons (hey its not clothes exactly), a hula skirt, lei, and coconut bra, or cereal boxes (or unfolded beer cases) done up as a loin cloth.