When I was battling someone I used sleep powder and the affected poke woke up immediately and then I battled this person again and the poke woke up right away with one of the pokes and then another one in the same battle. Somebody please explain.
Sleep Powder just causes sleep, and sleep can last from 1-3 turns in Generation 6 and 5 (1-4 in Generation 4, 1-6 in Generation 3 and 1-7 in Generation 1)
Source: http://bulbapedia.bulbagarden.net/wiki/Sleep_Powder_(move)
http://bulbapedia.bulbagarden.net/wiki/Sleep_%28status_condition%29