Spread onion slices evenly at the bottom insert of slow cooker. Trim skin and any excess fat from pork and place over the onion. Pour in ginger ale. Cover and cook on low until meat is very tender, about 8 hours.

Remove pork from the slow cooker and place on a large dish. Using two forks, pull the meat apart. Drain the onion and place on a small bowl. Discard the liquid from the slow cooker.

Whisk together apple jelly, ketchup, vinegar, Worcestershire, Tabasco, garlic powder and ground ginger in a large saucepan, then set over medium-high. Bring to a boil, whisking, until apple jelly is dissolved and sauce is smooth, 6 to 8 min.

Add shredded pork and onion to the sauce in the pan. Stir until all meat is coated with sauce. Remove from heat.

Serve on toasted Kaiser buns with coleslaw.