Can you have coffee on the MC?

I suspect I know the answer to this, but don't want it to be true. I have two coffees in the morning (with milk) and until yesterday it didn't occur to me that that might be verboten. Yesterday and today I only had one... do I have to give my coffee up? Sigh... what about soda? I am addicted to Diet Coke, but once again I have a feeling that will be not OK. What about Diet Sprite or Decaffinated Diet Coke? PLEASE don't take my soda away!!!!!