Combine 1 cup each of sugar and water in a saucepan over medium heat. Stir until the sugar is completely dissolved. Reduce the heat and simmer for about 5 minutes. Remove the pan from the heat and stir in 1 cup each fresh lemon juice and lime juice. Allow it to cool before bottling. Store it in the refrigerator.
Alternatively, combine 1 cup each of sugar and water in a cocktail shaker or a bottle with a tight seal. Shake until the sugar is dissolved. Add 1 cup each of lemon and lime juices, bottle, and refrigerate.
You can also combine one part of pre-made simple syrup with one part lemon or lime juice to create a last-minute sour mix.
