Oh, dear.... This can now go in all sorts of directions. What's the difference between 'a storm in a cup of water' and 'a storm in a glass of Budweiser'? (Rhetorical question from someone who likes strong beer not made with rice, maize, etc.) I suppose the answer has something to do with polluting the water.
Seriously, I'd never heard the coffee-cup one either, though I do vaguely remember encountering the German version once.
Cheers,
R.