Used to express that the speaker of the 'sure call' doubts that a statement made by a person who he/she is talking to is truthful. often used in an elongated and loud tone, the longer and louder the sure call, the more doubtful the speaker is of the validity of the claim.
-"I'm sorry i couldn't make it over to your house last night, I felt sick..."
"Suuuure! I bet you really went and hung out with your girlfriend..."