Well if you worked where I do you would pay something like $4.00 or whatever ridiculous price the vending machines are charging right now. Price gouging fascists. But if we're talking a standard $1.25-1.50 here I don't see how you don't pick the mystery can. Sure you could get stuck with something awful like Dr. Thunder or some sort of RC Cola, or worse, club soda. But there's always the chance that you strike it rich with a Mellow Yellow or Jolt (orange flavor only, the rest sucked), or my all time favorite counter culture soda, Wild Cherry Pepsi. That'll create some jealous looks.
If someone other than me was crushing a mellow yellow while copy and pasting excel sheets while I'm stuck with a Fanta (how is that not one of the mystery options) I'd talk so much shit about their job performance and how they must have it in with some of the higher ups or slept with the right person. I'd honestly rather know someone less deserving got a raise than me snagging some kinda Jones Soda while Timmy from HR hits the jackpot with the Wild Cherry Pepsi. It's pissing me off just thinking about it (could just be because I'm thinking of HR).