my mug is a white styrofoam cup. when one starts to get discolored, it is tossed out for a fresh one!!!
Sorry I didn't explain. When I reread my post I might not have been clear.
The cleaner and more inert the container, the more your taste buds start detecting chemicals. When you ingest chemicals, the body gets accustomed to them.
Once I got a British Berkefeld Royal Berkey purifier a long time ago, my tap water started tasting awful. However, my health improved. There's not a hospital full of medical Drs in the country who would have figured out the cause of my health problems. They could have charged a hundred thousand dollars for tests and drugs/ chemicals and only made me worse.
Rather than going that miserable route, I used my own God given taste buds, personal records, and the knowledge God Himself provided to cure what ailed me. He gets the credit as the great physician.
Next, when using glass or ceramic (no lead glaze) mugs, eventually you will taste styrofoam as your built in detector gets recalibrated for those polyurethane chemicals. For non lead mugs, buy American made. Chinese is too risky.
Stainless has the benefits of durability if you use it for traveling, but the first two are best.
Enjoy your coffee.☕🙂👍