Ditch the coffee or soda before you enter your interview. If you need to fuel up, do it before you get to the interview.
Not only is it unprofessional to enter with a drink in hand, but during your interview, you should be focused on the task at hand: making a good impression, answering questions, maintaining eye contact with your potential employer, and paying attention throughout the entire interviewing process.
Having a drink in front of you creates the opportunity for distraction - fiddling with the cup, or missing a question while taking a sip, for example. And although it may be a relatively unlikely possibility, bringing a drink into your interview also gives way to other unsightly accidents - like spilling the drink on the desk, on you, or even your interviewer!
