Bet any person in the bar that you can light a cigarette, take three drags from it, blowing out smoke after each drag, and ashing after each drag, and after the three drags, the cigarette will be the same length as an unlit cigarette (of the same brand).

Sounds impossible, but actually very simple.

Put the cigarette in your mouth and grab the front of the cigarette with one hand (to ensure you don't light the front). Then simply light the cigarette in the middle, take your three drags, do as you promised and whoala.