Mahalo has a list of the best fictional brands, starting (resaonably) with ACME and including an assortment of advertisers both memorable and obscure.
Mooby’s, Hudsucker, Brawndo….
But they are all recent. I think the oldest ones are Hudsucker and, oh, there’s Soul-Glo from the ‘80s movie Coming To America.
Spoofing advertisers pre-dates the ’80s, though. I imagine it dates approximately to the, uh, first advertisers.
Heaven Can Wait (the original) featured the Strables who were…pork kings? There was a jingle for “Strable on the table” that Don Ameche liked to mock. Or his grandfather did, perhaps.
Rod Serling liked to skewer advertisers, though he never really paid them back for trashing his shows. I remember distinctly the contempt dripping from Static, where inane commercials for chlorophyll accompanied equally inane programming. (The protagonist rushes to his magic radio, which plays 20 year old radio programs. Heh. Radio commercials were awesomely stupid, too, but nostalgia is nostalgia.)
Just off the top o’ my head….