Why do your thermos stink?

Thermos containers can develop unpleasant odors due to the buildup of bacteria, mold, or residue from past contents, especially if they're not cleaned properly. If liquids, particularly those that are acidic or high in protein, are left in the thermos for extended periods, they can contribute to lingering smells. To mitigate this, it's important to clean the thermos thoroughly with soap and water, and to ensure it dries completely before storing. Regular maintenance can help prevent odors from returning.