The rules are simple: Choose any number of any kind of items you decide to insert into the vending machine's slot. A different user will have to decide what shall come out of the vending machine and then shall insert another item or items, and so on.
Example wrote:User 1: I insert a coin into the machine.
User 2: A soda is dispensed out of the machine.
I insert a ladybug into the machine.
User 3: The machine spits out the ladybug and says, "For the last time, quit bugging me!"
I insert a severed finger into the machine
All right, let's see what you can do!
... Oh yeah, me first...
I insert Mr. Krab's first dollar into the machine.