I dont drink (BH) and I dont smoke (BH), but as a Bochur I know that if you Assur EVERYTHING you will turn a lot of guys off. Look at the adults who went crazy over the Asifa! All remember what happened with The Big Event and Chasunah Takanos? Lay off a little.
And about drinking, you adults even Assured it on Purim from Bochurim! Calm down!
And in my Yeshiva, the most I ever saw was 6 empty bottles of beer (in a Yeshiva of over 250 Bochurim)