If your washing machine is smelling less than fresh, pop in a dishwashing tablet. NOT the gel packs or anything else that has a plastic covering. Run the machine empty on the hottest, longest cycle. These tablets are designed to cut through grease, limescale, and more which is what causes the odor. If you do this once a month and keep the washer door open between washes, it’ll be worth the price of the dishwasher detergent and you’ll be all set!