Tenderize the chicken thighs with your favorite meat tenderizer (see mine in the post), on both sides.
Place chicken thighs in a gallon-sized Ziploc bag, set aside.
Combine marinade ingredients in a medium-sized mixing bowl and whisk together until sugar dissolves.
Pour marinade over chicken, press air out of the bag, and seal tightly. Refrigerate overnight (or at least 4 hours).
Remove the chicken from the bag and place in a bowl; set aside.
Pour the marinade into a medium saucepan, bring marinade to a simmer and simmer for 5-10 minutes.
Place chicken on a medium-high grill and brush some of the hot marinade over the top (do not place brush back in marinade after brushing the chicken).
Continue to grill chicken until done (165 degrees internal temp) on both sides. TIP: If the chicken is really thick, you will want to grill it on medium heat.
Place cooked chicken in a baking dish and pour some (or all) of the hot teriyaki marinade over the top. Sprinkle with finely chopped green onions. Serve immediately on white sticky rice or with stir fy!