Bob is walking along minding his own business, when he comes upon Charlie who is in trouble; either having car trouble or being pursued by thugs or having lost something. Bob then takes it upon himself to help Charlie out of whatever pickle he is in. After that, Charlie is so grateful to Bob for his help that he gives him some food that he has with him, either a candy bar or a cookie or any kind of edible foodstuff.
Initially, this trope is Exactly What It Says on the Tin. A character is given food for his kind and selfless actions to the bystander in trouble. Expect this trope to show up in a lot of media.
Compare Food As Bribe, Tastes Like Friendship. Contrast Denied Food as Punishment.
A Dunkin Donuts commercial claims that its iced coffee is sufficient reward for a friend coming to help move.
This Whataburger ad which airs from Thanksgiving to Christmas.
Tubby also receives this treatment in an episode of the Little Lulu anime after inadvertently finding Lulu's pop's lucky gold piece in the mud, while making a mud cake to pass off as a real cake ( He and the others ate the entire cake that was intended for Lulu's pop).
Par for the course in Toriko, since the food's what they're after in the first place.
Subverted in Balto where Steele frames Balto by throwing sausage links that he stole himself from a butcher shop at Balto. The butcher blames Balto for stealing the sausages then promptly rewards Steele with the sausages that he stole himself. That Steele is a complete jerk.
There is a Clifford the Big Red Dog book where Clifford is rewarded with some meat by a meat truck driver after helping him with his truck while looking for Emily Elizabeth.
Invoked by Ciaphas Cain in Death Or Glory; after spending the entire novel leading an epic trek to safety through Ork infested territory he's pleased to realise that the regiment that's been sent to meet his group of ragtag survivors is Valhallan and promptly asks for his long awaited cup of tanna.
Exalted: Sidereals working for the Bureau of Destiny receive their salaries in the form of Ambrosia and Quintessence. Both are edible and delicious. Young Sidereals are advised not to eat their paycheques.
In Fallout: New Vegas, several quests end with the offer of free food or drink. Thanks to the need to eat in Hardcore Mode and the Hyperactive Metabolism otherwise present in the game, this often amounts to free healing. For instance, helping save a wasteland rancher couple's mutant two-headed cows earns you ten pounds of steak, good for at least 300 points of health.
In Sam And Max Hit The Road, the Bigfoot shaman rewards Max with his prized medallion after he and Sam save the day; Max wastes little time in unwrapping his reward and wolfing it down.
Similarly, but more useful in the long term, there's a couple of side-events in Tales of the Abyss where you get recipes for helping people out. Cooking can be an important game mechanic for healing up between battles, so it's better than it sounds.
Kingdom of Loathing: The reward for clearing the cellar of the Typical Tavern is three glasses of Typical Tavern Swill, equivalent to a basic mixed drink (which can further be improved with the Disco Bandit skill Advanced Cocktailcrafting). Also, the final reward for finishing the side quest given from Inside Degrassi Knoll are a half-dozen Mushroom Fermenting Solutions, which can possibly be crafted into epic-level booze, some of the best in the game, depending on what mushrooms you ferment.
In this game, edibles are an important part of gameplay (they allow you to get more done each day and may help you level up) so these are actually quite useful rewards.
ADOM: the reward you get from the Tiny Girl for rescuing her puppy from a scary cave? A piece of candy. The actual reward is the cave itself - it's a good place to train your stats, and has a guaranteed vault at the bottom.
In Ōkami, various characters offer you food after you've helped them out. Some, however, request that you wait until it's night.
In the Animal Crossing games, sometimes the villagers will give you fruit that is foreign to your town as a reward for doing them a favor.
Subverted in one episode of Doug, where Doug finds an envelope containing a huge wad of money. Everyone (including the police, who give him back the envelope after it goes unclaimed for a whole month) tells him to keep the money, but he eventually discovers it was lost by a slightly loopy elderly woman. He does the right thing and returns the money, and she rewards him for his good deed with a pack of chewing gum.
In The Critic, Jay discovers that the Oscar statuettes are actually chocolate.
"Now I want one even more!"
And yes, he does eat one.
At the end of the Mr. Bogus episode "Kung Fu Campout", Tommy offers a slice of cake to Bogus and Brattus, even after their attempts to claim the cake for themselves end up to naught. Justified, since Tommy probably did it as his way of thanking his two miniature companions for keeping Ratty and Mole away from the cake.
This is very common in the more traditional parts of the U.S. It is understood that when you enlist a gang of your friends and acquaintances for some big task like moving or yard/farm work, you will at the very least provide lunch or dinner.
Beer can be a 'currency' among friends for small favours.
In Canada, a case of beer is a usually unstated automatic reward for helping someone move, fix their car, name your task that takes a good few hours out of a day.
"I'll give you beer if you edit my paper" is not an uncommon sentence among university students.
Lollipops at the doctor's office. Alternatively, the jar of sweets on the teacher's desk.
Going out for pizza or ice cream after winning a ball game or getting an "A" on one's report card.