So I was thrilled to see Vox tackle the issue on Saturday:
...all the sources on the [Jonestown] massacre say the powder was the grape variety of another drink brand, Flavor Aid. Made by Jel-Sert, Flavor Aid appeared in one of the first newspaper reports on the massacre. The claim is repeated in the 1982 book Raven: The Untold Story of the Rev. Jim Jones and His People. And surviving witnesses said that Flavor Aid was the drink used, not Kool-Aid. With the evidence so clear, why did the phrase "drinking the Kool-Aid" emerge? Mental Floss suggests Kool-Aid's role as being a genericized name for all flavored drinks, the popularity of The Electric Kool-Aid Acid Test, and other factors made it easier to remember "Kool-Aid" than "Flavor Aid."I hope this helps educate the world that me saying, "Whoa, that guy really drank the Flavor Aid, amirite?" is not weird (though still insensitive).
Up until now, the main source of information on this topic was the Flavor Aid Wikipedia page, which wasn't maintained with the most rigor.
Kudos to Vox.