Looked into this for you. The vending machine only appears after day 25, once you've had the dream that reveals the Deity. You can trigger the dream by attending "Sundae Service" at the church.
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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!