Barbecue sauce is a thick sauce used to brush on meat, poultry or fish during grilling or baking to add flavor and retain moisture. The sauce is usually prepared with tomatoes or a tomato product, brown sugar or molasses, vinegar, onions, mustard and garlic. It may be prepared at home or purchased bottled. Because its high sugar content can cause charring, barbecue sauce should be used during the last 10 to 30 minutes of cooking. Additional sauce may be served with the cooked meat, but for food safety, sauce leftover from brushing should not accompany the food after it is cooked.