The only substances you need in b-school are:
1. Caffeine
2. Alcohol (optional).
B-school isn't some Asian prep school where you get a bunch of overanxious kids trying to outscore their peers by 0.001%.
It doesn't work that way. Even with schools that don't have grade non-disclosure.
B-school and business by extension is about people first and foremost. Relationships. Conversation. Spending time with people in group situations - whether at work or play.
You don't have to drink at all, but you have to be comfortable in social situations where people are drinking.
Business school can be hectic but not in the academic sense. You don't need to be hopped up on supplements. The most important things in b-school:
(1) Be a team player. Give more than receive. Help others. If you have a rep for being helpful to others, karma has a way of paying you back. You attract people. People love being around helpful individuals. This isn't about smarts or cognition, it's about your attitude. You'll be amazed what your fellow classmates will do for you if you get a rep for being a helpful person yourself - you WILL save yourself a lot of time on academics because of this. Again, no matter which school you go to, your classmates will be very supportive of you if you are supportive of them.
(2) Don't be a douchebag. Don't be that annoying person sitting in the front of the class pestering the prof with ridiculous and unnecessarily detailed questions, holding back the class discussion because you want some miniscule issue clarified for your own sake or to show that you're like "smart". Don't be the guy who can't see the forest from the trees. Don't be the guy who tries so hard to impress himself on guest speakers/recruiters that you are known as a shameless brownnoser.
Follow these two things, and it trumps your smarts or your grades. Moreover, you just need to put in a reasonable amount of effort to get okay/decent grades (and the experience ain't about grades). None of these things has anything to do with your cognition -- it's about character.
In business school more than any other grad school perhaps -- your classmates value your character far more than your smarts. You'd think that MBA programs are the Church of Capitalism, but at many b-schools it feels like a hippie commune
And at certain points it starts to look like one when a number of the dudes stop shaving and grooming becomes optional.
Remember that MBA students often get job leads from their fellow classmates. So even during recruiting, don't think that somehow that it's about your cognitive abilities or getting that extra boost. It's about being that person that people want to help out because you've been that helpful guy in the past.
Save the supplements for the Japanese cram schools, Chinese "buxiban", and Indian JEEE exam prep.
In b-school, so long as you're eating relatively well, sleeping okay, and drinking water, you don't need performance enhancing supplements.