The thoracic spine produces 90-95%of all your rotation (only 5-10% comes from the lumbar spine) so the best way to improve your movement is with rotation-based exercises.
Try all of these, in order and do 8-10 on both sides.
Andrew Clark is a father of 3 and the owner and principal physiotherapist at Clinical Physiotherapy, St Ives. He graduated with a Masters degree from the University of Sydney in 2010 and has since had 10 years experience working in musculoskeletal private practice. He has undergone extensive professional development and has experience treating a wide variety of patients and musculoskeletal conditions.