That's a common and frustrating problem! A lingering smell in your outdoor trash can is often caused by trapped residues and bacteria. Don't worry, with a few simple steps and common household items, you can get it fresh again.
First, empty the can completely. Hose it down to remove loose debris. For a powerful clean, create a paste using baking soda and water, scrub the interior surfaces, and let it sit for 30 minutes. Baking soda is excellent for neutralizing odors.
For a disinfecting boost, mix a solution of one part white vinegar to one part water (or use a diluted bleach solution: 1/2 cup bleach per gallon of water). Scrub the entire bin, especially the bottom and sides, with this solution. Vinegar cuts through grease and kills germs, while bleach is a strong disinfectant.
Rinse thoroughly with your garden hose and let the can dry completely in the sun before putting a new bag in. Sunlight is a natural deodorizer and disinfectant.
To prevent future smells, sprinkle a handful of baking soda at the bottom of the can before each new bag. Also, rinse food containers before tossing them and try to keep the lid securely closed. Performing a deep clean every few months will keep odors at bay for good.