You did the right thing. You should NOT partake in any food or beverages. They will only get in your way. You should eat and drink prior to the interview. If you are really hungry or thirsty you cannot focus! You should also avoid taking coffee in the car or the train. Aside from creating “coffee breath” you also risk spilling it on your clothes.
Also avoid eating any candy or gum, even if they are right in front of you. No matter how tempting it might be, you don’t want to get caught with your mouth full. And don’t get one on the way out either.
If you are a smoker, try not to smoke after you are dressed, or showered for that matter. The scent of cigarette smoke may work against you. If you have to smoke, do it outside of your car and brush your teeth or use breath mints prior to going into the interview. Smoke only in the designated areas of the building, and ask someone if you are not sure where that is.