I like the idea, but the gameplay is a bit too simple and easy. The 3-of-a-kind mechanics is a nice touch but would need some more other mechanic to make it more interesting. For example: the machine not only output random amount of drink, it also output random type of drink like a blue drink or a red drink, and the customers only drink one of them. This will present a risk for trying to save up the 3-of-a-kind bonus, and make the game more challenging. It's just a suggestion not criticizing, I know game jam is time-limited so games tend to be simple.
I noticed that this is your first game on the profile, so good job on finishing a game!