Occasionally (although rarely) a drink may leave a slight odor in a cup. Certain smelly drinks or acidic beverages such as coffee may leave a slight odor, but that can be remedied with a thorough washing or soaking your product in a bath of water & white vinegar or water & baking soda. A fresh slice of lemon left overnight can help too.If these methods don’t work, we will replace your product. Email us at support@Silipint.com.