put sugar and 1/3 cup of water in a small saucepan and bring to boil over high heat, stirring untill sugar is dissolved.

combine blueberries, strawberries, raspberries, and lemon juice in a blender and pur'ee untill smooth, about 30 seconds. add 1/3 cup simple syrup and blend just untill combined. (save remaining syrup for another use, such as sweeting iced tea.)

transfer pur'ee to popsicle molds and freeze 4 hours. insert popsicle sticks and freeze an additional 4 to 6 hours, or until frozen solid.