In a small skillet, stir-fry the cabbage in 1 teaspoon oil for 2 minutes or until tender. Remove and keep warm. In the same skillet, stir-fry onion and garlic in remaining oil until tender. Add the shrimp, water and soy sauce; stir-fry for 2-3 minutes or until shrimp turn pink. Stir in cilantro and pepper flakes. Serve over cabbage.