There is quite a bit of confusion over what this stuff is, yet tons of drinks call for it. Basically, Sweet & Sour Mix is sugar syrup combined with lemon juice, lime juice or both.
To make mix 3 parts sugar and two parts water, heat gradually to let the sugar disovle, then let the mixture cool. Once cooled add 1 part juice and mix well. This should last a few weeks in the fridge and makes yummy margaritas.