Bang Bang Chicken Kebabs

Name: Bang Bang Chicken Kebabs
Ingredients: 1 1/2 pounds skinless, boneless chicken breast, cut into 1 1/2-inch pieces; 3/4 cup buttermilk; 1/4 cup plus 2 tablespoons sriracha, divided; 1 red bell peppers, cut into 2-inch wedges; 1 green bell pepper, cut into 2-inch wedges; 1 onion, cut into 2-inch wedges; 8 mushrooms, cleaned, stems removed; 1/3 cup sweet Thai chili sauce; 2 Tablespoons soy sauce; 1/2 cup mayonnaise; 1/2 teaspoon onion powder; 1/2 teaspoon garlic powder; 2 Tablespoons cooking oil of choice, for oiling grill grates; 2 green onions, thinly sliced; 1 lime, cut into wedges, optional