I'm not suuuuure. Derren Brown made this girl drink a glass of vinegar like it was water. Glug glug glug, just like that. I wouldn't do that for a laugh even if there was an entire theatre of people watching me.
I wonder does being hypnotised fuck up your brain chemistry at all? Strikes me that it can't be good for someone, being put into a trance for several minutes - even if they do say it's like sleep.