Depends how much. I know people who have drank a lot or smoked a lot before exams and they ended up throwing up/passing out in exams. Doesn't seem like a very good idea. I guess if you were overly stressed, a small amount of alcohol couldn't do any harm...
I went into general studies stoned out of my head and im not joking it helped me
I wrote about Bob Marley and world peace but i was a bit paranoid to start off with
I dont think u should drink if the exams important, its gonna slow you down when ur tyring to think.
I'm not sure.. this sounds like it has some sense to it.
Playing the scenario out in my head, I can imagine having a weeny little drink (NOT like a pint or something!!) may be enough to relax you and get you thinking straight rather than "ohmygodwhatisthisexamohyesit'st hisandthisandIneedtorememberthis andohmygodi'mgoingtofail"...etc.
It is obviously not a good idea. Especially if you do it a few times to calm your nerves and it works, you'll soon find that psychologically you need a drink to calm down before every exam... then it will become before an important interview, and soon anything and everything important and stressful!
Smoking on the other hand does give you a biological advantage, but the risks are becoming addicted to cigarettes!
Ultimately, it may be best revising a little bit harder than trying to smoke and drink your way through exams.