The trick is to bend the cigarette without breaking it.

First challenge your mark to try and bend a cigarette without breaking it. It can't be done. The cigarette will always break.

Then take the bill ( you can use the bill as a bet) and roll the cigarette very tightly in the dollar bill. Bend the cigarette inside the bill and show that it is completely bent. Now unroll the dolar bill and show that the cigarette is still intact.

I've won quite some money with it because smokers know you can't just bend a cigarette.