I insert some change/money/coins/whateverkind of money from wherever.
*inserts yen*
The next poster tells me what I got and inserts more money.
Melodicanth got... a banana!
*inserts quarters*
Let's say I reply next.
Poster #2 got... a shoe!
*inserts a dollar*
I add that banana I already got form the machine to my Inventory.
Inventory:
A Banana
Maybe do a little bit of text or something.
Example: "Bananas: Best. Fruit. Ever."
And so on and so forth. Rules are obvious. Don't make the vending machine shove out things that will directly affect another person's already-owned item without their consent. Like, don't have the machine spit out a needle that pops the poster above you's balloon. Instead, have it pop out a needle, and gently hint "Hope it doesn't pop your balloon!" or some such. No godmodding, basically.
Here we go!
*inserts 20 francs*