In a small saucepan, combine cornstarch and sugar. Stir in the broth, soy sauce and vinegar until smooth. Bring to a boil; cook and stir until thickened, about 2 minutes. Set aside and keep warm.
In a large bowl, whisk flour and eggs until smooth. Stir in the bean sprouts, crab, onions, garlic powder and pepper. In a large skillet, heat oil. Drop crab mixture by 1/3 cupfuls into oil. Cook until golden brown, about 2 minutes on each side. Serve with sauce.