I have not done everything an actor could do on stage. But I have in fact appeared in my underwear before. I have had to kiss on stage, and I have had to pretend like I was going into a sort of respiratory distress.
Not to mention singing, during my occasional musical.
Yet despite all of this, the thing I hate to do on stage the most while I am trying to perform, is eat.
Yes. Simple as that. Eat. I hate the very notion of having to consume anything while acting. I consider it a distraction, and potentially dangerous, given that projecting one's voice to performance levels does not allow the throat to behave in the same way as it might when conversing over the real life dinner table. I feel vulnerable, and slightly less in control when food is involved. I avoid it whenever I can while doing a show.
I have been lucky thus far. Very obvious consuming of food has not yet been integral to any productions I have been in. I had to do it once as a student, and One scene in a play I was in a few years ago did take place at a dinner table.
My advice for those of you who also share this dislike for theatrical meals.
1) If blocking allows it, mask the food, so that the utensil does not actually remove anything from the plate. This allows you to place an empty fork or spoon in your mouth. This of course is easier for smaller items, or liquids, like soup. If it is not soup, chew, (VERY lightly of course!) on your own tongue. It will provide enough resistance to appear as though food is actually being chewed. Miming with nothing in your mouth will provide some of the most foolish looking chewing, even for the stage, than you can possibly imagine. Better to not even try to chew, than to chew air.
2) Bait and switch. Repeatedly make as though you are going to take a bite of something, just before you have a line. Then interrupt to motion and deliver your line. It's true to real life, for those who do not like to talk with their mouths full, and in most cases people will only be looking right at you when you deliver a line anyway. When you are not the center of attention, make like you are cutting something between your moments of dialogue. Audiences will likely be looking at the speaker at such times anyway, but you are covered if they do not.
3) If applicable, take tiny bites. This is a no brainer.
4) You you cannot take small bites, remain in character while wiping your face with a napkin, and remove the food into that if you can. This is not the cleanest way, but again, it allows the audience to see you are acknowledging to food in front of you, without you having to swallow it and digest it later on.
5) If none of these things work, or none of them can be put to use in your particular scene and you must openly consume some food, make sure you eat some of what you will be eating backstage, before the scene. Have the sample be as close to how it will be on stage as possible. It begins digestion earlier, and will customize your mouth and throat to what is coming.
I love food and I love theatre. Yet to me, the two don't mix. I have found, with these tricks, they rarely have to.