Instead of using baking soda or other abrasive tool to remove coffee and tea stain, here is a quick and simple tip to keep the mugs and cups clean. The same technique can be used on cast iron pots with ceramic coating or even the smooth surface of the stove top / tiles, granite counter top.

Where to buy:
The Melamine Sponges can be bought from the below links or Daiso Retail Stores
http://www.daisojapan.com/p-26726-melamine-sponge-16-pcs-20pks.aspx

Mr. Clean Magic Erasers