Most hackers don't smoke tobacco, and use alcohol in moderation if at all. However, there has been something of a trend towards exotic beers since about 1995, especially among younger Linux hackers apparently influenced by Linus Torvalds's fondness for Guinness.
Limited use of non-addictive psychedelic drugs, such as cannabis, LSD, psilocybin, nitrous oxide, etc., used to be relatively common and is still regarded with more tolerance than in the mainstream culture. Use of `downers' and opiates, on the other hand, appears to be particularly rare; hackers seem in general to dislike drugs that make them stupid. But on the gripping hand, many hackers regularly wire up on caffeine and/or sugar for all-night hacking runs.