Sour mix, also called sweet and sour mix, acts as an important and integral ingredient in a range of cocktails. Sour mix is also important when you're creating your own signature mixed drinks -- with the rule equal parts liquor and sour mix invariably resulting in a drinkable libation. If you don't have sour mix, you can use other items to complete the drink while maybe adding a little zing or fizz to the finished cocktail.

To mimic sour mix's sweet and tart flavors, it's best to go to the source with either lemon or lime juice. Although either juice by itself -- or the two combined -- will be too sour, mixing either a single juice or a combination of the two with a sweeter juice, like orange or pineapple juice, will help tone down the sourness. Juice-based products, like lemonade, limeade and margarita mix, will also work well as substitutes -- if the finished drinks are too sweet, add another splash of fresh lemon or lime juice.

Some sodas will cover up the fact that the drink's missing sour mix and will also add some sparkle. The simplest soda substitute is a lemon-lime soda, and other near substitutes include ginger ale, orange and club soda. For each soda substitute, add some fresh lemon or lime juice to increase the tartness of the drink. Combine different sodas for a more similar taste, such as half lemon-lime soda and half ginger ale or equal parts lemon-lime, orange and club sodas -- both with a splash or two of fresh citrus juice.

Some sour mixes in bars and restaurants come from a sweet and tart powder that's then mixed with water. A few powdered substitutes that can work in a pinch are powdered lemon- or lime-flavored beverages, including lemonade, limeade and energy drink powders. Other powdered beverages that will work well include pink lemonade and fruit flavors, like orange and blood orange, as well as powdered margarita mixes. Powdered mixes are also simple to prepare because you only need to mix them with water. Powdered mixes often have low-calorie and low-sugar versions.

Do-it-yourself sour mix is both quick and simple and requires less than a handful of ingredients: simple syrup, which is a sweet mixture of 1 part each sugar and water, and lemon and lime juices. Pour the water into a saucepan, then bring to a boil. Reduce the heat to a simmer, mix in the sugar, and stir until it is fully dissolved. Turn off the heat, remove the saucepan, then allow the contents to cool. Mix equal parts of the cool simple syrup with lemon and lime juice to make a homemade sour mix, which will keep for up to two weeks in the refrigerator.