What can I eat pre-show?

Hello! I have an upcoming musical. I've been wondering if there's a substitute for coffee/energy drinks since it's on one of our 'don'ts' for cast members-- which I understand, considering drinking coffee before rehearsals does make my mouth feel heavy.

My role isn't very physically taxing, but it does require me to sing a lot. Would adrenaline be enough to keep me awake during the show, or is there anything I could eat on the universal 'do not consume' for singers? + Do you have anything you like to eat/drink before rehearsals? Thanks in advance!