Combine the sugar and water in a medium saucepan over medium-low heat. Stir occasionally until the sugar has completely dissolved. Add lime juice and stir to incorporate. At this point you can either portion out and freeze for future use or chill the hot mixture in the refrigerator until cool. When you are ready to use it, simply add 2 cups of cold water to each cup of limeade concentrate. Stir and Enjoy!