Talking to BA Cabin Crew over the years at times when their tongues were loosened with alcohol (not rare occasions!), it struck me how many proudly bragged, or knew of someone, who had 'fixed' pilots drink or food because of perceived sleights or whatever! I was absolutely staggered that people could be so stupid, but from the number of reports, I know it happened, and some of the old dragons would not shirk from doing it to pilots they disliked. I know for myself I have experienced sudden and explosive, and instantly vanishing, stomach upsets (and inflight!). Fortunately I have retired from that institution with no apparent lasting damage, but just possibly slightly radioactive, but not due to cabin crew 'food additives' I think!
Yes it does happen, and no, nobody is interested!