Can I drink coffee/eat before my first injection?

Hello! I am getting my first shot tomorrow and trying to mentally prepare (chronic spontaneous urticaria/unknown and non-specific food allergies). Is it recommended to avoid caffeine before/during injection monitoring? I have unfortunately trained my body to get headaches without coffee but I'm really scared about whole thing but especially the tummy troubles side of the possible (but unlikely(trying to hard to convince myself of that)) anaphylaxis. Do you guys eat and drink normally when you get your injections???? Thank you!!