The easiest, but also probably the most expensive, is just to get a pet food or barnyard animal food dispenser that has a remote and then use a SwitchBot to automate that remote. There are some of these that are used for animal training. Of course you’d also have to find candy that fit that device. If you don’t mind candy not being wrapped, M&Ms would work fine. 
2020 Switchbot Review ( robot button pusher), integration through IFTTT or new V3 app
But if you don’t have any of that equipment already and you don’t have any other uses for it, that could easily be a $300 solution. Easy to set up and automate, though. 
This is the treat dispenser I already use with my dog. It works very well. I was already thinking of putting it inside a large plastic jack-o’-lantern with the tray sticking out. 
. The remote is about the size of a poker chip and the dispenser is about the size of a football helmet.
Since I already have the treat and train and the Switchbot, it won’t cost me anything except a plastic pumpkin. 
. And I will probably use about four dollars of Sugru to stick it to a table by the door. But obviously it would be expensive if you were starting from scratch.