Heat oven to 400°F. Place wire cooling rack in 15x10x1-inch pan.
Cut each chicken wing at joints to make 3 pieces; discard tip. Cut off and discard any excess skin.
In large bowl, stir together sweet-and-sour sauce and Sriracha sauce. Remove 1/4 cup of the sauce to small bowl; set aside. Add chicken wings to remaining sauce; toss to coat. Place chicken wings on rack in pan.
Bake 25 to 30 minutes, turning once, until chicken is no longer pink in center.
Toss baked chicken wings with reserved sauce. Sprinkle with onions.