A scourer with hot water and dishwashing liquid works great.

I use salt and rub with my fingers

I use bicarbonate of soda, cheap and easy, but my mother in law uses bleach.

tried the salt on the scourer which dose work but requires a lot of elbow grease to remove brown marks however I found that my laundry powder works a lot more effectively on the scourer pad and brings it back to bright white. It requires less than half the effort and I use it on my roasting dishes and other dishes that need to be thoroughly cleaned after use. Then just rinse well afterwards for a streak free finish.

I use EXIT Mould only takes a few minutes and then I wash very thoroughly either by hand or pop in the dishwasher. This method works a treat.

Hi I use Gumption on all my coffee cups, casserole dishes etc with a white non abrasive scourer. hope that helps. I have included a pic so you know what to look for. It will last for ages.

Buy cheap denture cleaner tablets from the supermarket…homebrand ones will do…pop them in the mugs and they should get them lovely and clean.

Having the same trouble myself too! so annoyigng!

Brown coffee marks in cups put some bio carbon soda inside the cups and some hot water to soak leave in cups for as long has you can then wipe out with a dish cloth.

Rub salt with wet sponge on the stain.Then rinse.

I meant to add that before I discovered these magic things I used Jif too.

Too easy! Buy a Chux magic eraser. (White sponge thing with blue on one side). Wipe around cup. Gone. Rinse. Done. Also good for tarnish on silver, ring on bath etc. They really work but they look disgusting as soon as you use them. I just hide min under the sink!

Gumption. Buy it from supermarket. Cleans anything and you only need a tiny bit

If they are really bad try putting a cap of bleach into cup and wash with water. Rinse Well before using again. Looks like a brand new cup after. Good for tea stains too.

Bicarb , works like a dream, for cleaning too.