1. Mix soy sauce, 1/4 cup water, vinegar, sugar, ginger and half of garlic in a small saucepan over medium heat. Whisk constantly until sugar is dissolved.
2. In a small bowl, whisk together 2 tablespoons warm water with cornstarch until well combined. When sauce reaches a full boil, reduce the heat to medium-low. Slowly whisk in cornstarch mixture and simmer until thick. Remove from heat and set aside.
3. Heat vegetable oil in a large skillet over medium-high heat. Add onions and cook until translucent. Add turkey and garlic and cook until turkey is just cooked. Add carrots and broccoli and cook until vegetable reach desired texture.
4. Pour teriyaki sauce into the skillet and stir to coat. Turn the heat to low and simmer while you cook the noodles according to package directions.
5. Serve stir-fry mixture over noodles, hot and garnished with green onions.