Well, generally it's about a person being reincarnated as a vending machine. There are various adventures and interactions that follow as the vending machine tries to survive in a strange new world. It has some unique concepts like dealing with different customers and the challenges of being an inanimate object in a living world.
The main character is, of course, the person who is reincarnated as a vending machine. There might be other characters like the customers who come to the vending machine, some of which could be important for the story development.
The novelty. It's not every day you see a vending machine as the main character in an isekai story. It's a unique concept that immediately grabs the reader's attention.
Once upon a time, there was a magical vending machine in a small town. A little boy named Timmy approached it. When he inserted a coin, instead of the usual snacks, a tiny animated fairy popped out. The fairy thanked Timmy for freeing her from the vending machine's magic. She then granted him a wish. Timmy wished for all the kids in town to have free ice creams from the vending machine for a week. And so, it happened, and the vending machine became the most popular place in town.
A vending machine could be the portal to another world. For example, a girl inserts her coin, and instead of getting her drink, she's sucked into an animated world full of talking snacks. She has to find the 'exit - coin' to get back to her world. Along the way, she befriends a chocolate bar and a bag of chips who help her in her quest.
This anime was called "Midnight Story Vending Machine." The male protagonist liked to go to the beach to observe the starry sky, while the female protagonist bought drinks in front of the vending machine, only to find that she couldn't get a drink by tossing a coin. This was also part of the plot of the novel. I hope you like this fairy's recommendation. Muah ~๐