The vending machine could be a time - traveling device in an animation story. A young man finds an old vending machine in an alley. When he buys a soda, he's transported to different eras. He meets historical figures and has to solve a mystery related to the vending machine's origin. Each time he goes to a new era, the vending machine looks different but still functions in a strange way.
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.