Having felt iffy all evening at a jazz gig in Berkshire, I had to put my bass down mid-tune to run out and projectile vomit all over the toilets - sink, floor, mirrors etc (I was told I could be heard). Then, feeling like s***, had to clean it up. I then went to sleep in the van, convinced I was dying.
Food poisoning (I don't drink or do drugs).
Band finished without me and, to their credit, I still got paid.