One of my biggest dislikes OP. Why, oh why, does everyone needs to be constantly drinking or eating on the move. Just sit down for a few minutes for goodness sake, it will do you good. Or, shock, horror, wait until you get home, back to the office to have a drink. You won't suddenly drop down dead for lack of liquid/sustenance. I know I am old, but we used to survive outside, in all weathers, for several hours, before we came in for our tea/dinner.
Great. I'll tell I'll my fellow primary school teaching and staff members that grabbing food on the run when we're on break or at lunch when we're actually still sorting out problems and working is wrong and to knock it off. OH, and hey, if we don't drink, we won't have to worry about needing the toilet during lessons! 
Rude word off.
Yes, we eat and drink on the run, literally, because we often don't have 10 minutes to sit down quietly to do so ... always children there waiting for something to be done for them, or being interrupted to sort something out, or being asked to run clubs on breaks, etc ... so we grab food when we can and carry water/drinks.