Alka Seltzer – Fill the thermos bottle with water, next drop in 4 Alka Seltzer tablets in. Allow it to soak for an hour (overnight for tougher jobs) clean as you normally do.

Arm & Hammer – Fill our thermos with 2 cups hot water and 2 tablespoons Arm & Hammer. Seal the thermos tightly and shake vigorously. Remove the lid and allow it to it overnight. In the morning clean as normal.

Cascade Dishwasher Detergent – Apply 2 tablespoons Cascade into the thermos with hot water to the top. Allow it to soak for 30 – 60 minutes. Then using a bottle brush clean well.

Effreident – Apply 2 Efferdient tablets and fill the thermos with water. Allow it to sit overnight and clean as you normally would in the morning. Use a bottle brush to get all surfaces.

Bleach – Apply 1 teaspoon bleach and fill the thermos with water. Allow it it for about an hour and then clean well with a bottle brush. Then air dry. This is also the best way to deodorize your thermos. via