Some find it helpful to take a sugary snack and a drink of water (especially during long sessions),in case they feel faint or dizzy.Your blood sugar can drop and your adrenaline hit (the same is also true when you get pierced) and a bite of something can help you to feel better.
However,I agree with the other answer,posted in response to this question,that most artists would not appreciate a client (or those that they are with) messing up their studio with food and drinks,just for the sake of it: it is not an appropriate place to have your private party.
Win ;)