Never had to do a gig with the flu or food poisoning. That sounds awful!
Yeah, it's no fun.
About 8 years ago, the band I was in had a high profile gig at a popular venue, we were opening the show for a regional act that could bring in a big crowd. Two days before the show, I got the flu, big time. Throwing up, high fever, body aches, chills, and so on. I was a wreck. There was no way I wanted to cancel the gig, I figured I could get well enough to play provided I get enough rest and try to flush it out with fluids. Gig day comes around, and I feel better, but still feverish and having difficulties keeping solid food down. Showed up to the venue, did sound check, and still had about 90 minutes to rest, so I went out to my car for a power nap, and then have a quick bite to eat before show time, hoping that I don’t toss it back up, though if push came to shove I had placed a large plastic bucket back by my rig so I could run back and barf if I had to. The show starts, and we did very well, great crowd response and I had a some folks on my end of the stage cheering me on, so that helped keep me going. I felt like I was playing the show drunk, definitely still feverish. Other than some bits and pieces, and a moment where my guts were giving me some issues (which my drummer didn’t care for at all), I really don’t remember much about the actual gig.
Another one, but this wasn’t me, it was my guitarist. This was back in 1995, I believe, and we were playing a gig at a place with a rather high stage. During load in, my guitarist jumped off the stage and he said “ow!”, but he seemed to be ok, he was walking fine, so we didn’t think anything off it. First song of the set, we get to the guitar solo. I’m rocking out on my side of the stage, I hear the guitarist go into the solo and then it sounds like he’s just smacking the thing around. I turn to look and he’s trying to pick himself up off the stage, and failing badly. His left leg isn’t working for him at all, he can’t stand and he’s all tangled up in his cords and pedalboard. We stop the song, I go over to him and he says that his knee did go out on him, and he’s in massive pain. I tell him “Ok, we’ll get you to the hospital” and he says “No! Get me a chair, some advil, and a glass of scotch”. He played the rest of the gig in the chair, and he rocked out. He got some massive props from the crowd for that. The next gig the following weekend, he played the gig in a rocking chair with the arms removed. I think he had surgery sometime after that.