You can serve this orangeade on its own as a nonalcoholic beverage, or use it in the orange shandy recipe.
Bring sugar and 2 cups water to a boil in a small pot. Reduce heat; simmer, stirring, until sugar dissolves. Remove from heat; stir in coriander and orange zest. Cover, and let steep 2 hours. Simple syrup can be refrigerated up to 2 weeks. Strain before using.
Combine syrup and juices in a 3-quart pitcher, and refrigerate until cold, at least 2 hours and up to 2 days. Serve over ice.