I've noticed that my coffee cups are getting stained. Neither myself nor the dishwasher can get the stains out. Any suggestions? (Other than buying new cups ;)
Baking soda. I use a standard dish sponge/scrubbie with baking soda and a little water and it comes completely out. I've actually tried it with just a damp paper towel and baking soda and it's almost as easy.
Baking soda has natural whitening properties and is a very gentle abrasive. I actually started using it elsewhere (sinks, counter tops, greasy pans) before discovering its use in coffee cups.
I've also tried baking soda + salt on counter tops and pans with great success. Salt has similar whitening properties (surprisingly to me) and is a stronger abrasive. Haven't tried it in coffee cups, but you might consider trying that if you need a little extra cleaning power. (Also: Aside from being cheap, baking soda / salt are food-grade and non-toxic!)
Another possibility for residual stains: Try soaking in powdered dishwasher detergent (i.e., stuff for automatic dish machines, not dish soap) and boiling water.
The process: put a small amount (~ 1 tsp / 5 mL) of powdered dishwasher detergent in the cup. Fill cup with boiling water (very hot tap water might also be okay). Stir to dissolve detergent. Let sit for at least 1 hour or overnight. Empty, rinse, wash with sponge or scrub brush and conventional dish soap as usual.
I did this to clean my heavily tea-stained equipment, and it worked great, as I noted in another question and answer of mine from Seasoned Advice.
This stuff cleans stains from all my presses, thermoses, and cups...makes all like new again.
Use some thick household bleach with the option of adding a bit of warm water.
Leave this to stand in the cup making sure the stains are coated with bleach. After leaving these for several hours the stain will eventually be removed! Works on the toughest stains.
Remember: wash this out thoroughly under a tap before using it!
I nice clean cup or mug certainly adds to coffee drinking enjoyment in my opinion. Since coffee stains are somewhat oil based, I suggest you put in a dollop of coconut oil, sprinkle in some baking soda, salt, and a few drops of water, scrub with a toothbrush or nail brush. Follow with some vinegar, then a hot water rinse. Since your cup is warm it is a perfect time for another cup of coffee :-)