Things You'll Need
Sponge or cleaning brush
Over time, coffee leaves a strong smell in your frequently used travel mugs. This is due partly to the strong smell of the coffee itself, but a bigger reason why your travel mug clings to the smell is because it's so difficult to thoroughly clean that narrow space. After all, the regular mugs in your kitchen don't smell like that! That said, the key to getting rid of that stale coffee smell in your travel mug is to use a good cleaning solution to destroy the faint residue causing the smell.
Wash the travel mug with soap and water like you normally do. Use a sponge and/or a brush to wipe it down the best you can. Rinse off the soap with hot water.
Heat some water over the stove until it begins to simmer. Fill up the travel mug halfway with baking soda and then fill it the rest of the way with the hot water. Stir together and let sit for 30 minutes.
Rinse the mug out and let it dry.
To remove coffee stains from the mug, mix three parts baking soda with one part water to make a cleaning paste. Rub the stains with a sponge or a toothbrush. Rinse with water. Repeat as necessary.
Use baking soda to clean your mug once or twice a month to keep it fresh.