Serve tonight: Combine first 4 ingredients in a gallon resealable freezer bag; seal. Toss to coat. Place bag in a shallow dish and refrigerate 1 hour or up to overnight.
Preheat grill to medium. Remove chicken from bag; place marinade in small saucepan over medium heat. Bring to a boil. Whisk together cornstarch and water; slowly whisk into marinade until it reaches desired consistency. Set aside.
Grill chicken, brushing with marinade and turning occasionally, 25-30 minutes or until internal temperature reaches 165°. Makes 6 servings.
Serve with vegetable sticks and a slice of watermelon.
Freeze for later: Combine first 4 ingredients in a gallon resealable freezer bag. Seal well, label and freeze. Thaw completely. Prepare as directed above.