Spitting in the Customer's Food

If you're an Unsatisfiable Customer or otherwise not Nice to the Waiter, this is how he may get back at you. It's not just limited to spit, either... as Real Life incidents have testified to over the years, an especially vindictive server may adulterate a customer's food with other bodily secretions -- or worse, any inedible or possibly poisonous substances he may find handy. And sometimes it happens not to get back at a particular customer, but at any or all customers, For the Lulz or even For the Evulz.

Finding out this has happened may prompt an I Ate What? response from the diner in question.

While Real Life incidents are not explicitly excluded from this trope, please keep in mind the Rule of Cautious Editing Judgment, because some cases start at Squick and get much, much worse. Also, do not list examples of food adulteration born only of greed or depraved indifference -- this trope is explicitly about contaminating served food as a kind of revenge, either on an individual or a group.

A Sister Trope to Tampering with Food and Drink, which sometimes overlaps with it.

Examples of Spitting in the Customer's Food include:

Comic Books

In Persepolis, for a while, the author has to wait tables in Austria. When one of the guests molests her, the cook sneakily avenges her by spitting on his schnitzel.

Fan Works

In chapter 7 of the Crossover fic Harry Potter and the Vegas Mishaps by "alienyouthct", there is this exchange between Harry and Hermione:

"Strong words from the girl who relied on the tea I brought her to stay awake long enough for Astronomy class."
"You mean the tea that enslaved elves made for you?"
"Hey, Dobby was a free elf. All the other elves would spit in drinks if they knew it was for you."

In the Harry Potter Alternate Universe fic Hermione Granger and the Boy Who Lived (part of The Teraverse), Hermione spends some time working undercover as a servant in the UK's Spy School Harworts (sic), where she learns that the kitchen staff routinely spits in the food that Drake Malenfant sends back "to be prepared properly".

Film

In Waiting, a "beeyotch" makes the mistake of pissing off the waitstaff. In response, the cooks put pubic hair, dandruff, and spit on her food. One guy even rubs the garlic bread in his pants and all over his penis and testicles. And made it so that she doesn't even know what she's eating.
In the movie Fight Club, there are several references to people urinating or worse into food.

"Tyler was now involved in a class action lawsuit against the Pressman Hotel over the urine content of their soup."

In Road Trip, a waiter licks a pancake and stuffs it down his pants before serving it. The customer, oblivious to the prank, cheerfully eats it, saying it is the best he has ever had.
The name of the Mexican restaurant that appears in Anchorman: The Legend of Ron Burgundy is very clearly shown to be "Escupimos en su Alimento" -- Spanish for "We Spit In Your Food".

Literature

In re-prints of the novel Fight Club, Palahniuk adds a foreword. In it, he notes that many ex-waiters told him that tampering with food was Truth in Television, including one man who claimed to be a former waiter at a 5-star London restaurant who bragged that Margaret Thatcher had eaten his semen five times.
- His subsequent novel Choke has a character based on that waiter, complete with soup urination.

Live-Action TV

Referenced in an episode of 3rd Rock from the Sun. Disguised alien Dick initially doesn't tip waiters because he doesn't know he's supposed to. When he's told about the practice, he declares, "No wonder my coffee always tastes like spit!"
In the Friends episode "The One With the Racecar Bed", Rachel admits to adding body fluids to the drinks she serves to people who don't tip her sufficiently.

Music

Bob Rivers parody "Minimum Wage" begins with a client asking for a Spiffy Burger, "...and curly fries, but only if they're cooked in virgin peanut oil..." in an upper-class, sophisticated aristocratic British accent. It ends with the minimum-wage worker spitting in his food and telling the client to "enjoy your burger!"
Invoked by Eminem in "The Real Slim Shady" as an example of the contempt felt by him and his Expies for most other people:

And every single person
Is a Slim Shady lurking
He could be working
At Burger King,
spittin' on your onion rings

Western Animation

In the 2019 Big Mouth Valentine's Day special, during the scene where the restaurant goes into chaos, one waitress confesses how she spits in the customer's food and doesn't even know why.

Real Life

There is an urban legend in the UK about somebody getting sacked by McDonald's for having A Date with Rosie Palms in a burger.
A disgruntled coworker was caught on hidden camera urinating into the office coffee pot.