A reference to the 1978 cult mass-suicide in Jonestown, Guyana. Jim Jones, the leader of the group, convinced his followers to move to Jonestown. Late in the year he then ordered his flock to commit suicide by drinking grape-flavored Kool-Aid laced with potassium cyanide. In what is now commonly called "the Jonestown Massacre", 913 of the 1100 Jonestown residents drank the Kool-Aid and died.
One lasting legacy of the Jonestown tragedy is the saying, “Don’t drink the Kool-Aid.” This has come to mean, "Don’t trust any group you find to be a little on the kooky side." or "Whatever they tell you, don't believe it too strongly".
The phrase can also be used in the opposite sense to indicate that one has embraced a particular philosophy or perspective.
Alice: Hey, did you hear that Joe is working on the Nader campaign?
Bob: Yeah, he really drank the Kool-Aid on that one.
Chris: I'm thinking about attending a PETA rally
Donna: Whatever you do, don't drink the Kool-Aid!
To completely buy into an idea or system, whether good or bad.
Coach Bellichick got his players to drink the kool-aid.
Going along with what a crowd desires. Often used when a person changes positions on a topic.
Dave got a haircut and a new suit. Looks like his company is making him drink the kool-aid.
To make a wholehearted, unconditional commitment (to some group, or idea, or plan) in contrast to choosing an alternative. It emphasizes a resolute decision (good or bad) in response to a choice.
This is a reference to the "electric Kool-Aid acid tests," which were LSD parties held in the San Francisco Bay area in the mid 1960's. Someone who was willing to drink the LSD-laced Kool-Aid had, symbolically, made a choice to join (if only for a few hours) a counterculture that stood against conventional society. Once you take acid, you're committed -- the trip lasts for hours and you can't cut it short or change your mind. Once you've drunk the kool-aid, you're firmly committed.
IMHO it is not about suicide: kool-aid isn't a symbol for poison.
Coach got his players to drink the kool-aid.
I really like Macintosh computers; I've totally drunk the Apple kool-aid.
That berserk guy who tried to kill people at the Tides Foundation really had drunk the kool-aid that the right-wing media were serving.