Each vending machine encounter is divided into three sections:
The grab - In the first stage, click the mouse when the lung meter reaches the middle (arrows will appear when you should click). Clicking early or when the meter indicator is in the red may result in a fatality or affect the behavior of the machine in the next stage.
The pound - In the second stage, click the mouse on the targets to shake the snack free from the machine.
In later stages, it will take multiple clicks to clear each target (indicated by concentric circles).
The finish - For the final blow, wait until the machine is level with the ground and the words "Hit Now" appear on the screen. Click when "Hit Now" is on the screen to deliver the final hit and enjoy your snack.
You have to want it.