For me as a singer, I eat really little earlier in the day, although I try to gauge what will help me not pass out/have decent energy and stamina versus what will make me heavy and crappy-feeling onstage. I spent this whole last week with some old rocker friends, and some days rehearsal was like 3 pm and later, going onstage like 10 pm, and so I could see what there was to eat (at a resort, so it was not all in my control), like small calorie-dense stuff (hummus etc.) to have early, and a ton o' water all day. I don't drink booze, so that helps me bigtime calorie-wise, and really, after a gig, I may be so wiped I eat maybe a yogurt with flaxseeds in it to keep digestion going, my vitamins, and call it a night. It gets tough when I do it five days in a row like this last week at this party, so that meant that EVERY day I had to look okay and be ready to rehearse etc., so no food got eaten really all week. Just my version of it as it worked out recently--!

Don't let the fact that it's free make you feel like you deserve it or that you're missing out on some sort of gig-bonus if you pass up a free beer for a free diet drink.
If you think there is no "safe" food at the gig; Brown bag it.
Our environment is overloaded with the wrong foods. If you think it's too hard to find it, BRING it with you.
There's usually decent food to be found at a wedding gig, but the Sammy's BBQ Bar gig is probably not a safe-food paradise.
Sure, the high-cal food and beer might be free for the taking at the gig, but we'll pay for it, one way or another, if we accept it.

I'm a singer so I eat light/high energy during the day but not too close to gig time.

I have one or two drinks (JD and diet coke usually) but stick to water for the majority of the night.

I am pretty good on gig nights, I'm generally too busy to worry about food/drink too much. :P

I have a stomach a size of a peanut because of the stage fright, so I mostly drink water before a gig. After the gig is another story