2)can be used in a just kidding sort of way
Girl: "My hair is gorgeous!"
Girl's Sister: "Sike Naw! It's hideous!"
Boy: "I'm giving my Wii away for free!"
Boy's Friend: "For real?"
Boy: "Sike Naw! Your not getting that Wii!"
1. To negate a previous statement.
2. To express sarcasm.
3. To express disagreement with someone else's previous statement.
"The Boilermakers are sweet. Sike naw, they're terrible.
"I should spend Saturday night hanging out with my parents. Sike naw."
"I say sike naw too much."
"Sike naw, no you don't."