In a large skillet, brown the chicken and onion over medium high heat until chicken is no longer pink. Add the garlic and cook for 30 seconds.
Reduce heat to medium, add the sugar snap peas, rice wine vinegar, soy sauce, hoisin, sesame oil, ground ginger, sriracha, and chile pepper if using. Cook for just a few minutes or until sugar snap peas are to desired tenderness. Add salt and pepper to taste. Serve warm plain or over rice.