While a Thermos offers a great way to keep soups or hot beverages hot until lunchtime, a stinky Thermos may make you want to think twice before using it again. Whether the odor is from fragrant foods or a lunch left in it too long, a regular washing combined with some baking soda or a little vinegar can get it smelling fresh once again.
Air it Out
It's all too easy to forget about that Thermos after consuming its contents. If it has been sitting with the lid on for a day or longer, that Thermos probably smells of whatever it previously contained. This is particularly bad if the food has spoiled.
To begin the cleaning process, remove the lid, swish some warm water around inside the Thermos, then dump the water out. Let the Thermos air out for several hours or until you're ready to wash it. Sometimes, a quick rinse and fresh air are enough to deodorize the container.
Washing the Thermos with warm, soapy water is sometimes enough to remove lingering odors. Put a small squirt of dish soap in the carafe, then fill 2/3 of the way with warm water. Replace the cap, swish the Thermos around a little, then dump the water out. Rinse, then sniff the Thermos again. If it still reeks or doesn't look clean, sprinkle a little baking soda inside while the Thermos is still wet. Scrub the inside with a dish cloth wrapped around a bottle brush to help loosen debris. Rinse the inside of the Thermos, as well as the lid, but don't soak the parts in water. Wipe the outside areas off with a dish cloth.
Vinegar offers an all-natural way to remove odors from Thermoses, travel mugs and water bottles that are difficult to clean. Pour an inch or two of white vinegar into a clean carafe, then fill most of the way with hot tap water. Place the lid on the Thermos, shake it up, then let it sit for 30 minutes or so. Empty the Thermos, then allow the vinegar to air dry. The remaining vinegar helps remove any lingering odors, and eventually evaporates without a trace. Rinse the Thermos if the smell is gone, or repeat the vinegar soak if not.
The best way to keep that Thermos odor-free is to always rinse or wash it immediately after use, or at very least, within several hours. The longer liquids sit in the Thermos, the greater the chance they'll spoil and stink up the container, or even worse, get moldy.
When it comes to soups or other foods, its best to store those in a Thermos device designed specifically for food. These have wider openings than the traditional beverage-style Thermoses, and they're also much easier to clean. A traditional Thermos has a narrow mouth, so it can be difficult to remove caked-on residues.
After washing any kind of Thermos, let all the parts air dry instead of placing the lid back on while the parts are wet. This helps eliminate any slight odor that may remain in the Thermos.