Place a dishwasher-safe cup filled with plain white vinegar on the top rack of the dishwasher. Using the hottest water available, run the dishwasher through a cycle. The vinegar will help to wash away the loose, greasy grime, sanitizes, and helps remove the musty odor. Next, sprinkle a cupful of baking soda around the bottom of the tub and run it through a short cycle. The baking soda will help freshen and removing stains.