Step 1Heat 2 tablespoons of oil in an 8-inch skillet over medium heat. When the oil is hot, add the red and green bell peppers and garlic. Cook over medium-low heat, uncovered, stirring often, until the peppers are tender, about 25 minutes. After 10 minutes, add the water, salt, pepper to taste and the red pepper flakes. When cooked, stir in the vinegar and sugar. Remove to a plate and keep warm.
Step 2Add the remaining tablespoon oil to the skillet and heat over medium heat. Add the shrimp in batches and cook, stirring often, until the shrimp are opaque, about 3 to 4 minutes. Do not overcook. Remove the skillet from the heat. Add the parsley. Taste; adjust seasonings. Spoon shrimp over peppers. Serve warm or at room temperature.