Prep: 3 minutes; Cook: 5 minutes; Stand: 5 minutes; Freeze: 3 1/2 hours. If you want to skip the layers, add the total amount of buttermilk and orange juice to the sugar syrup and freeze the mixture for 3 hours.
Combine sugar and water in a small saucepan; bring to a boil, stirring constantly. Boil 30 seconds, remove sugar syrup from heat, and let cool 5 minutes.
Mix 1/4 cup buttermilk and 1/4 cup sugar syrup in small bowl. Pour equal amounts of buttermilk mixture into 8 pop molds. Place molds at an angle (try tilting them in a large plastic container); freeze 1 1/2 hours.
Whisk together remaining 1 cup buttermilk, remaining sugar syrup, vanilla, and all but 2 tablespoons orange juice concentrate (reserve for last step). Remove molds from the freezer, and add the juice mixture and pop sticks; freeze 1 1/2 hours.
Remove molds from the freezer, and distribute reserved 2 tablespoons orange juice concentrate among the pops; freeze 30 minutes or until firm.