Pour the 1 1/2 cup water into the saucepan, then place it on a stove burner on high. Allow the contents to boil, adding the sugar and stirring till it dissolves completely. Remove the saucepan from the stove, and allow the liquid to cool.
Pour the saucepan's contents into the container, then add the lemon and lime juices. Seal the container and shake gently to mix.
Set the container into the refrigerator for about two hours to chill before use. Store your sour mix in the refrigerator for up to a week.