Hey there!
What version of the game are you playing? The vending machine isn't available in the demo, but unlocks on day 25 otherwise.
Viewing post in Worshippers of the Gain comments
My apologies, I was remembering an earlier build of the game. In your tablet in-game, there's a piece of blue text you can unlock for each character by talking to them. Once you have all 9, and you've done Sundae Service, you'll get the first dream and the vending machine should unlock the next morning. Sorry for the confusion!