In a mixing bowl whisk together honey, soy sauce, olive oil, garlic cloves and red pepper flakes if using until well combined.
Place shrimp in a gallon size resealable bag or a shallow dish. Pour marinade over shrimp, seal bag while removing excess air. Rub marinade over shrimp and transfer to refrigerator and let marinate 30 - 60 minutes.
Note if using wooden skewers soak in water at least 30 minutes so they don't burn up.
Preheat a grill over medium-high heat to about 400 degrees.
Thread shrimp onto skewers. Clean grill grates and brush with oil.
Place shrimp on grill and cook through, about 2 minutes per side.
Sprinkle with green onions or parsley if desired and serve.