All nighters occur for many reasons: Boredom, inability to sleep, or approaching assignment deadlines are just some of these reasons.
At a guess, an average compsci pulls 2/3 all nighters per assignment deadline.
After an assignment deadline, weary compscis go down one of two paths....they go to bed...or they go to the pub!
An energy drink of some form is a good way to fight off the tiredness. For this reason, compscis usually make a trip to Spar/CKs and stock up on Relentless/other high energy drinks.