Drinking coffee from a mug while riding on the trainer is difficult. The coffee sloshes around. Its tricky. But I think perseverance is key. You, meaning at least I, gotta keep on training your/my coffee drinking on the trainer. Why bother? Why not just give up? Because coffee is awesome, and riding is awesome (even on the trainer its way better than say, golf), so riding while drinking coffee must be awesome too. In fact, it does not just sound good on paper, its also sounds good in practice; I like to slurp. When riding the trainer in the early morning drinking coffee at the same time just makes sense. The question is: would it be cheap/too easy to use a spill resistant travel mug? I think that's cheating, it would take the whole art out of it. No, you have to use a regular mug and go for it. I bet some people can drink their coffee while on rollers. Having only a couple hours total on rollers in my lifetime, I think I'll leave that to the experts.
Who else drinks coffee on the trainer (or, gasp, rollers)? Anyone? Beer? Hmm, reminds me of Tom Green's experiment. Cable TV gold that was.