If it were up to me;
To combat the obesity epidemic, a motherly voice would issue from candy machines when particularly bad junk was selected. After all, what's the good of a chocolate bar if you don't feel shamed while eating it?
Four words, Co2 powered can rockets.
There would be a joystick on the vending machine that you use to guide your delicious treat through a randomized labyrinth. If you fail, James Earl Jones will laugh from a speaker above as your candy bar is vaporized. Your fifty cents? Lost forever.
Button A1 would always be fabrege eggs, the coin bucket would be expanded to allow up to $75,000 in quarters to be deposited. Also a small hand brush and dust pan will be available for retrieval of egg.
Vending machines that dole out mean spirited advice from spiteful friends, like "Dump the dumb hussy!" and "Car payment, shmar payment, lets hit the casino!".