Marinade the chicken in the teriyaki sauce for at least 30 minutes, or overnight. Drain and blot dry with a paper towel.
Heat the oil in a large skillet or wok. Cook the chicken in the hot oil, stirring frequently, until the chicken is no longer pink. Add the garlic and vegetables and cook an additional 5 minutes, or until tender.
Stir in the Szechuan sauce. Top with the peanuts and chopped cilantro.