Sour mix is a common cocktail ingredient made from a blend of lemon or lime juice and simple syrup. It provides a balanced tartness and sweetness, making it a popular choice for drinks like Whiskey Sour and Margaritas. Sour mix can be purchased pre-made or easily prepared at home. Typically, sour mix consists of equal parts fresh citrus juice and sugar syrup, though variations may include additional flavors or ingredients. It enhances the taste of cocktails by adding a refreshing zing, making it a staple in many bars and restaurants.