Nope. Very much real, if perhaps defunct.
Do you mean the original Yoyodyne, or Buckaroo Banzai’s ripoff of the name?
How about Filboid Studge ?
Poop Soda from Invader Zim:
Gir: “What kind of drinks you got?”
Crazy Taco cashier: “Poop, Diet Poop, Cherry Poop and Poop Free.”
RealityChuck , a Saki fan! God, I love his work. One of my cats is named Tobermory, for the cat in the story of the same title. And Clovis is one of my favorite characters in fiction.
Sorry for the hijack!
Ren and Stimpy’s favourite breakfast, uh, thing, “Powdered Toast.” When you run out of it, you can call on its spokesperson and superhero:
**POWDERED…TOAST…MAAAAAAAAN!!!
Morley’s brand ciggarettes. X-files
It’s also a brand of boots.
Several great ones on “Futurama”, such as Slurm and Bachelor Chow (“Now with flavor!”).
And if you’re going to mention Powdermilk Biscuits (“Heavens, they’re tasty, and expeditious!”), you can’t forget Bebop Areebop Rhubarb Pie, and Bebop Areebop Frozen Rhubarb Pie Filling. Nothing takes the taste of pain and humiliation out of your mouth like Bebop Areebop Rhubarb Pie!
Dr. J
Rodbell’s
The main department store in the Lanford Shopping Mall.
From Roseanne
That’s what I thought, but a check of Google shows that a search on Stay-Puft Marshmallows (also Stay Puffed and Sta-Puft), that, outside of the endless Ghostbusters references, I can find no evidence that Stay-Puft marshmallows ever really existed outside of the movie. I did however, find America’s favorite brand of marshmallows, Jet Puffed, originally made by Kidd’s Marshmallow’s, until the rocket fuel plant next door expoded, and they changed their name to Favorite Brands International, which which was acquired by Nabisco, which was in turn acquired by Kraft Foods, which now has no reference to marshmallows at all in its listings of U.S. brands.
So, while it seems there once was a Jet Puffed Marshmallows, I think Stay-Puft is a confabulation we all misremembered.
There’s always the “Pineapple” computers on Digimon. Or “Soylent Green”, but I forget if that was the company’s name, or just the product’s.
Ranchoth
Red Apple Cigarettes, from various movies Tarentino has been involved with.
Powdermilk Biscuits from A Prairie Home Companion
.How about the Banana Jr. 2000 from “Bloom County”?
“Soylent” was the company and Green was a product, as was Red and Blue. There may be some others but I can’t remember.
“Wild Rebels Cereal”, from a host segment on MST3K.
There’s Soylent Red, Yellow, and new Soylent Green, but no Soylent Blue. Remember, Tuesday is Soylent Green day. 
When you’re in Sunnydale, California, be sure to visit Doublemeat Palace, the place where Buffy works.
S
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The ‘meat’ is actually made of vegetables.
From The Dark Backward: Blump’s Pork Juice and Blump’s Bacon In A Tube.
Yum.
Fear Itself - Jet Puffed marshmallows are still being made. I see them at the store all the time. They’re listed on this Kraft page under “Sugar Confectionery:”
I don’t know if there was ever a “Stay Puffed” brand. Sounds more like a pillow name to me.
Mmmmm, sugar confectionery.
Chatchkey’s in Office Space
Looks like the same cheesy kind of place as TGI Fridays and Ruby Tuesday, with the same cheesy waitstaff wearing suspenders and fake smiles.
Not exactly a product, but it’s kind of becoming an icon since that movie has such a cult following. At my job it’s becoming the lingo for “want to take a break?” – “Want to go to Chatchkey’s?”
The Queen Family Truckster from National Lampoon’s Vacation
“You think you hate it now? Wait 'til you drive it!”
I include the following for this thread, not because it’s interesting or amusing, but just in the interest of completeness:
“Shasa” sodas. I’ve seen these cans as set dressing on several different sitcoms; Roseanne comes immediately to mind. The logo on the can was made to look like that of the discount brand “Shasta,” but without the “T.”