You can dust and/or vacuum the inside of a sauna in between uses to remove dust, hair, dead skin cells, and dirt. Wash down benches or back rests with a natural brush dipped in diluted white vinegar and water or mild detergent diluted with water, taking care to avoid harsh chemical detergents that could leave a residue that could turn into fumes when the sauna is in use. Be sure to leave the sauna door open so that the surfaces can air dry after cleaning. Wearing towels in the sauna can help prevent sweat stains, but whether or not you care more about keeping your benches pristine or going au naturel in the sauna is up to you.