1. In a small saucepan, bring soy sauce and sugar to a simmer. Cook 2 min. In a large bowl, stir together soy-sauce mixture, vinegar, ginger, garlic and oil.
2. Cut chicken into -inch-thick strips (about 1-1/2 inches wide). Reserve 1/3 cup soy-sauce mixture, then add chicken to the remaining mixture and marinate in the fridge for 1 to 2 hrs.
3. Heat grill to medium. Discard marinade, then thread 1 or 2 pieces chicken on each skewer accordion-style; thread scallions crosswise onto separate skewers. Oil grill grates and cook kabobs, turning once, until scallions are soft (4 min) and meat is cooked through (8 to 10 min). Brush kabobs with reserved sauce. Makes 6 servings.