A classic lunchbox accessory that keeps liquids both hot and cold, thermoses are a common sight in schools and workplaces. Since thermoses hold a variety of drinks and foods -- such as coffee and soup -- it is not uncommon for the odors and tastes of previous contents to linger in them. These lingering odors can affect the flavor of liquids stored subsequently in a thermos. You can quickly neutralize such odors using common household items.
Fill a sink with warm, soapy water. Place the thermos inside the water and let soak for five to 10 minutes.
Wipe the inside of the thermos with a cloth dampened in the soapy water. Rinse the thermos clean with cool running water.
Pour 1 to 2 tbsp. of baking soda in the thermos. Add 1 cup of white vinegar and secure the lid on the thermos. Vinegar is an all-natural cleaner and deodorizer that can remove tough lingering odors inside a thermos.
Shake the thermos for several seconds. Remove the lid and pour the contents down the drain.
Rinse the thermos with cool running water and let it air dry. Repeat the process as needed.