Rinse it (and let soak, if necessary) with white vinegar.

If it is stainless steel, use baking soda and hot water.
If it is plastic, throw it out and buy stainless steel.

Ditto on the white vinegar--it's the only thing I've ever found that cleans/de-smellifies coffee residue effectively.

Denture cleaner works good. I used it once on a thermos that had 3yrs of coffee 'seasoning' in it. looked new the next morning after I rinsed it out.

I don't have a dishwasher at home, but I take my mugs to the office and wash them once a week in the dishwasher. It gets rid of the coffee smell until the next go. Other than a dishwasher, I don't know because I've had the same problem when handwashing!

The first rule to travel mugs: Never put coffee in your tea mug.

You can wash it however many times you want, but it'll never be right for tea again. I use a thermos for my coffee, and if I want tea, I keep regular mugs for it in the office.

Step one - wash in warm soapy water
Step two - dry with a towel
Step three - place in freezer (don't seal lid), and keep there until ready to use.

Putting some automatic dishwasher powder in it and filling it with water overnight might help too. That's what I usually do. But yes, it's so much better with stainless steel. Usually, though, they have plastic lids which will trap the coffee taste too.

I keep separate mugs for coffee and tea because I can never fully get the taste and smell of coffee out of a mug

white vinegar, baking soda and i second the denture cleaner. actually, the denture cleaner is fantastic for removing red wine stain from an antique crystal decanter and nothing else would touch it!

Stainless steel inside (oxo no leak) + Bar Keepers Friend = looking and tasting new after 5 years of daily use.

Use a 1:10 ratio of bleach and water, let it soak for a bit, then wash well with soap and water. Gets rid of any smells or stains. But really, I would not use the same mug for tea and coffee.

I also use hot water and white vinegar.

Spouse uses denture cleaner tablets in warm water in his travel mugs. One for water/cold beverages and one for coffee. He makes sure the drinking spout is in the cleanser too. Leave to soak and wait until the water color changes.

Denture cleaner also works for hummingbird feeders and coffee mugs.

dedicated tea mug is the answer! or ceramic.

My husband uses his stainless steel tea mug for coffee occasionally, and I have found the best cleaning solution is:
1. Mix 1 part vinegar to 3 parts warm water in the mug, add a splash of salt. (the salt just allows it to work faster)
2. Put the lid on and shake it around and let it soak for a few minutes.
3. Take the lid off and pour the mixture out on & around the lid & seals.
4. Rinse out with hot water.

We do the same thing to clean out our coffee pot!

Things I have learned is to never use soap on a stainless steel mug, and to not mix bleach with vinegar or any other acid - it creates poisonous fumes!

Hope that helps!

I have to say I've never found a good solution. (Will have to try some of the ideas here.) I ruined my two stainless steel tea mugs when I had some visitors and sent them out with my mugs full of coffee. I never could get the smell out and had to buy a whole new mug for my tea. :(

I have to second the white vinegar too. Leaving the lid to soak overnight in some pure vinegar gets the smell out every time for me.

Julia, I would suspect the issue might be with the lid. This has happened to numerous travel mugs of mine-- stainless steel, plastic and even ceramic! I realized the coffee odor is usually the lid, where you sip the coffee from.

If it's a stain in there, it might never be fixed :( . However, if it's an odor issue, i recommend pouring some boiling water with a dash of vinegar.

I don't know about you but soaking my travel mug in denture cleaner or vinegar everyday would be annoying. Just buy another travel mug. I keep one for tea and one for coffee and have never had an issue. Or like someone else said. Keep a mug at the office to drink coffee from? I highly recommend contigo travel mugs!

i personally dont think anything gets rid of that coffee taste. this might be annoying but i have two travel cups now...one for coffee and one for tea.

Go to your local starbucks, say you have a starbucks stainless steel mug and you can't get it clean, ask for have some of their stainless steel cleaner. It literally lifts EVERYTHING off of the stainless steel, just add some to water and let it soak over night, then wash thoroughly. We've been doing it for years. :)

I'll add to the chorus about the vinegar and the stainless.

BUT my other tip is to stuff your washed travel mug with some clean newspaper, put the cap back on and leave it for a day or so. Repeat with fresh newspaper as many times as you need. This works well on all sorts of stinky containers.

super hot water and put the lid on it to keep the heat in and let it soak.
I used to work at a coffee shop, if its stainless you could use the cleaner used for the espresso machine. The kind I know is called purocaf.

My favorite solution? Denture cleaner. It works like a charm for pulling out odors, grit, red wine stains and other annoying hard to clean bits of stainless steal, glass, etc. Buy cheap generic denture cleaner tablets, add 2 for a 16 oz cup, add water and let soak over night. Rinse well. Enjoy a fresh cup of tea.

Soaking vinegar in a stainless steel one has worked for me, but depending on the saturation of the smell, it may take a few applications to really get it out.

I place the plastic top of my travel mug with the drinking "spout" forced opened over a prong in the top shelf of the dishwasher. I place the cup, stainless steel, next to the top.

I would advise swirling some vodka. The alcohol will help dissolve the fatty oils contained in coffee. These are not so water soluble, thus the need for a less-polar solvent (alcohol)

Puro-Caff.

It's espresso machine detergent and will get out old and set-in smells and stains. You can get it on Amazon. I've worked in so many coffee shops and this stuff is great. Soak your mug in a mixture of scalding water and a few tablespoons of the powder (its abrasive so don't scrub with it or you'll open tiny scratches that will trap stinky, stainy oils and taint the mug worse in the future). Also, rinse your hands after it comes in contact with your skin. A little exposure won't hurt, but prolonged exposure will dry out skin and nails.

Cascade liquid cleaner and very hot, almost boiling water. Let it soak.