The product placement here makes the Subway plugs on Chuck, The Biggest Loser and Pawn Stars look like the pinnacle of subtlety:
A recurring feature of Seinfeld was its use of specific products, especially candy, as plot points. These might be a central feature of a plot (e.g. Junior Mints, Twix, Jujyfruits, bite size Three Musketeers, Snickers, NestlÃ© Chunky, Oh Henry! and Pez), or an association of a candy with a guest character (e.g. Oh Henry! bars), or simply a conversational aside (e.g. Chuckles, Clark Bar, Twinkies).
Non-candy products featured in Seinfeld include Rold Gold pretzels (whose advertisements at the time featured Jason Alexander), Kenny Rogers Roasters (a chicken restaurant chain), Oreo Cookies, Triscuits, Ben & Jerry's, H&H Bagels, Baskin Robbins, Dockers, Drake's Coffee Cakes, Ring Dings, Pepsi, Mello Yello, Snapple, Clearly Canadian, Bosco Chocolate Syrup, Cadillac, Saab, Ford Escort, Tyler Chicken (a parody of Tyson Chicken), Specialized Bicycles, Nike, BMW, Volvo, Toyota, Tupperware, Calvin Klein, Klein Bicycles, Ovaltine, Yoo-hoo, Arby's, TV Guide, Trump Tower, Glide Floss, Gore-Tex, Entenmann's, J. Peterman clothing catalog, and the board games Risk, Boggle, Trivial Pursuit, Scrabble, and Battleship.
The computers shown in Jerry's apartment are Apple Macintosh and several different models were shown, although Jerry is only seen using his computer once during the entire show. Also seen throughout the show's run were many different brands of cereal, e.g. Cheerios. Notable exceptions to this pattern are a fictional scotch brand called "Hennigan's" (a portmanteau of "Hennessy" and "Brannigans") and a canned meat product called "Beef-a-reeno" (a parody of "Beef-a-roni"). Product placement, for Snapple, was inserted as a parody of product placement; when offered some by Elaine in the middle of a conversation, the character Babu Bhatt's (owner of a Pakistani restaurant named "Dream Cafe") brother declines, calling the drink "too fruity". A second time this product was mentioned is when Marla "the Virgin" is offered a Snapple by Elaine.
The show's creators claim that they were not engaging in a product placement strategy for commercial gain. One of the motivations for the use of real-world products, quite unrelated to commercial considerations, is the comedy value of funny-sounding phrases and words. "I knew I wanted Kramer to think of watching the operation like going to see a movie," explained Seinfeld writer/producer Andy Robin in an interview published in the Hollywood Reporter. "At first, I thought maybe a piece of popcorn falls into the patient. I ran that by my brother, and he said, 'No, Junior Mints are just funnier.'"
but it doesn't really resolve whether this was all paid advertising or merely the use of real-world props.
Joan Crawford (then on the board of PepsiCo) telephoned director Billy Wilder to protest the movie's Coca-Cola connection. Wilder then added a final scene in which James Cagney buys four bottles of Coke from a vending machine. The last bottle out of the machine isn't Coke but Pepsi.
During Leno's Monday night (March 18, 2013) monolog, he joked that the introduction of the new Doritos Locos Taco at Taco Bell had created hundreds of new jobs...for plumbers. For those who didn't get the joke he mimed using a plunger. Both he and Conan are unrelenting with negative mentions of the chain but I doubt that it has hurt business.
Taco Bell won't sue. They love all the publicity, good or bad, they can get.