Does your garbage disposal smell like last night's dinner? Here's a recipe to kill odors and keep your disposal fresh. Flush your disposal with a mixture of water and ½ cup baking soda once a week. You can also grind citrus peels for a clean, fresh scent. NEVER use harsh commercial drain cleaners - they'll harm the machine. It's much safer to use the natural alternatives - they're inexpensive and right at your disposal.