A Fart
Especially one that sneaks out, slips out unintended (squeaks by). If it's wet, it's a Cheek Squeaker Shissle or Cheek Squeaker Drizzle.
(dude farts) "O shit, that was a cheek squeaker."
or
"I can't eat any more Wendy's, I've been launching cheek squeaker shissles all day."