Worst come up I ever had was on mushrooms, when I drank the mushy tea after drinking a pint of orange juice. I'd drank all the orange juice because I read on Shroomery that some people believed orange juice had some sort of action which made the trip more intense, but there was much split opinion about whether this was bullshit or not. Anyway I knew I was in for a rough ride when I felt like I was coming up fast in after only 5 or so minutes, and my friend who was doing it with me who had been for a shit during the first 10 minutes agreed that he seemed to be coming up far sooner than expected too. I felt really, really anxious and on edge and had the worst nausea ever; ended up throwing up several times with a stream of vomit that came out with the force of a fire hose. Think it was lots of chilli in my stomach that came up - definitely doesn't taste as nice on the way back up as it does going down! The trip was awesome after the come-up, however
Before anyone starts calling bullshit on the orange juice thing, all I can report is that it seemed to work for me and my friend - it made us have a quick intense come-up, and seemed to intensify yet make shorter the trip. I'm in no way trying to spread misinformation, it's just that orange juice did seem to have an affect on the mushies, could be down to placebo or some shit, I don't know, but it seemed to work for us