It would depend on how you're doing it. Is your opponents back to you or are you sitting in his line of site reaching over for your cup and bringing it up to your mouth and back to the table etc...? That would drive me nuts. I think if your opponent is facing you in any way shape or form that you should sit still.
The other thing, are you taking a drink of coffee or are you "sipping" it? Sipping makes noise. An irritating noise at that.
I wouldn't say that taking a drink of something is a sharking technique but things associated with it could be.
MULLY