Unfortunately, The Juice is not referring to the kind of cavity you get in your teeth. It’s a cavity you might use to try to smuggle drugs – in this case A LOT of drugs! As reported by The Jamaica Online Star:
The court was told that on October 17, approximately 3:10 p.m., [forty-three-year-old Kevin] Peart [from Birmingham, England] was preparing to board a flight to Birmingham at the Sangster International Airport, when an officer on duty noticed that he was behaving suspiciously.
If you were “carrying” what Mr. Peart was, it would be impossible to NOT behave suspiciously.