There's no accounting for taste. Still, you would like to know which cola your audience prefers: Coca-Cola, or Pepsi Cola? To this end, you have brought two cards where two identical glasses of cola are drawn upon.
On the backside of those cards, you can see which cola it is, because one of the cards clearly shows a can of Coca-Cola, while the other depicts a can of Pepsi Cola.
Your audience must simply point out their favourite drink, every time you shuffled the cards. Try as they might, and even though you only use two cards, nobody manages to find their favourite brand. You then put the card with the Pepsi Cola aside, so it must be very clear you are just holding the Coca-Cola. Or are you? You turn over the card, and instead of showing a can of Coca-Cola, a bottle of wine is now there instead. Quickly turn over the card again and show how the glass of Cola is inexplicably turned into a glass of red wine.
A funny "monte" with delightful attributes. Very easy to perform. A real showstopper.