Find The Soda

Looks like the Grey Labyrinth's visitors are getting smarter. We've had quite a few people find this puzzle too easy.

As most of you figured out, the contents of the machine can be determined with just one dollar. Since each button's label is always wrong, pressing the random button will tell you which it contains- the soda which comes out, always. The two remaining buttons must also be wrong, and with only two options left, the solution is clear.