In a small bowl, whisk the soy sauce, sugar, sesame oil, onions, vinegar, and garlic. Add the marinade to a zip top bag. Add the chicken and seal the bag.
Massage the chicken from the outside of the bag for 20 seconds, place in the refrigerator overnight.
Heat an oiled grill pan on medium high heat.
Cook the chicken for approximately 5 minutes on each side or until cooked.
Sprinkle sesame seeds over the chicken.
Recipe by Savory Sweet Life at https://savorysweetlife.com/easy-chicken-teriyaki/