In the late 80's/early 90's, when I was in college:
coke and mt.dew
In the mid 90's to late 90's, when I was working at a .com:
coke, mt.dew, jolt (and coffee was what the suits drank, one even commented about it: "guess your morning coke is like my morning coffee")
Since 2000, where I've been working at a university:
I've noticed a couple fellow geeks turn to coffee/tea/espresso a we've gotten older, but it's more of a "refined palette" and "moving away from soda for health reasons" type thing, than "more caffeine". But, the bulk of geeks I know are still getting caffeine from soda.
That goes for morning caffeine jolt, or all-nighter caffeine.
(the "22 years of geekdom" wasn't "since I've been alive 22 years", but "since I arrived at college, and realized my true place in the universe" ... I'm 40, and while I've always been a geek, I didn't really start to move past math/gaming type geekdom until I arrived at college, started my formal CS education, and had access to the 'net)