I too never eat before playing--just doesn't feel right for some reason. At the most, I might pick up a pack of mints on the way to the job, but that's about it.
This is an interesting topic and leads to one that I would also like to relate to other Synthzone members. I've weighed myself before leaving for a job and immediately after arriving home. Most of the time, after four hours of playing and singing, I'll loose on an average of 4 to 6 pounds. Obviously, this is fluid loss, but when I talked with my doctor about this he said singing for four hours would be similar to doing a four-hour workout and breathing heavily the entire time.
When you think about it, he's probably right. You lug a huge amount of equipment from your house to your car, then unload it to the job and set it up--not lightweight work by any means. Then, while singing, you must breath much deeper than normal and exhale much longer than normal, which essentially removes much of your body's moisture through evaporation from the lungs. At the end of four hours, you load the equipment back on the cart, take it to the car, then drive home and unload it again. I know guys who work on loading platforms that don't work this hard. In fact, they would life this stuff without a fork lift.
A little food for thought,
Gary