DURING THE TAKEOFF GROUND ROLL, THE PILOT NOTED THAT THE FUEL CAP ON THE WING WAS LOOSE AND FUEL WAS LEAKING FROM THE FILLER CAP. THE PILOT OPTED TO ABORT THE TAKEOFF AND APPLIED THE BRAKES. THE PILOT STATED THAT THE SOD RUNWAY WAS WET AND THE BRAKES WERE NOT EFFECTIVE. THE AIRPLANE BEGAN TO SLIDE AND GROUND LOOPED BEFORE COMING TO A STOP.