Add the water and white vinegar to a 6 oz. custard cup. Break egg into cup, pierce egg yolk with toothpick, and cover dish loosely with plastic wrap. Place in microwave and cook for 1 minute or until desired doneness. You may need to experiment with cooking times based on the wattage of your microwave and taste preference. Immediately remove egg from hot water with a slotted spoon as it will continue to cook. Serve with salt and pepper to taste.