If your bathtub is soiled beyond what a standard bathroom cleaner can handle, here’s a trick: Fill the tub with hot water and a gallon of vinegar. Let that soak for a few minutes. Then use a sponge to scrub the surface, using baking soda as an aggregate to loosen the stains. Fitting a fan in the bathroom can reduce the dampness that attracts dirt and mold to the tub and other surfaces.