Coffee and tea stains on mugs and cups are quite normal. And as you might have noticed these stains will not come off when washed on a dishwasher or by hand on the sink using washing up liquid. Now there are some solutions on taking these stains off, can use salt, baking soda, and white vinegar all together and rub it on the stained part of the mug. Or try putting a little bit of (clothes) washing powder on a sponge and rub it inside the stained part of the mug or cup. You can then see an instant result, but do rinse the mug or cup thoroughly!