Cleaning a metal thermos can be tricky, as the inside is difficult to reach with standard cleaning tools. Luckily, there are several ways to remove odors, stains and food debris from the inside of your metal thermos. Typically, soaking the container with warm water and various cleansing agents will do the job.
Warm, soapy water method
Rinse the metal thermos with cold water for three minutes, and then rinse with hot water for three minutes.
Wash with warm, soapy water and a bottle brush to remove any debris from the inside of the thermos.
Rinse again thoroughly before using.
Fill the metal thermos about a third of the way full with crushed eggshells.
Add one cup of hot water and put the lid on the top of the thermos.
Shake for about 5 minutes and then discard the contents.
Rinse well with hot water.
Baking soda method
Fill the container with warm water, and add 1 tbsp. baking soda.
Allow the metal thermos to stand for three hours. The baking soda will break up any debris inside the thermos during this time.
Wash thoroughly with hot, soapy water and rinse clean.
Dishwasher detergent method
Add hot water to the thermos until it is full, and then add 1 tsp. of automatic dishwasher detergent.
Allow the mixture to stand for about 30 minutes, and then wash thoroughly with hot, soapy water.
Rinse with cold water before using.