Great question! Their manufacturing team uses a food/beverage safe cleaning solution to rinse out each flask after the manufacturing process. To sanitize your flask properly before use and remove the smell, they recommend following the steps in the Flask Care Guide. For the screwtop, you can allow it to soak in hot soapy water for several minutes. If the smell persists after cleaning your flask, please repeat the sanitizing steps 1-2 more times. If the smell still persists after this, please contact our customer care team.