The pilot was performing touch-and-go landings, and during the landing roll, he removed his hand from the twin-engine airplane’s throttles to turn off the electrically-powered fuel pumps. As the pilot moved his hand, his sweater sleeve caught on the right throttle handle, the right engine power increased, and the airplane veered off the runway to the left. During the runway excursion, the airplane collided with a runway marker sign and visual approach lighting equipment, which resulted in substantial damage to the fuselage and empennage. The pilot attempted to reduce the right throttle setting, but his sweater was jammed between the throttles, and he ultimately stopped the airplane by shutting down the airplane’s engines. The pilot reported that there were no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation.