Why does my washing machine smell like mildew and how can I get rid of the odor?

Your washing machine may smell like mildew due to a build-up of mold and bacteria from moisture and detergent residue. To get rid of the odor, you can try cleaning the machine with a mixture of vinegar and baking soda, running a hot water cycle with bleach, and leaving the door open to allow the machine to dry out between uses.