In a small saucepan, heat blueberries, sugar and water over medium high heat until boiling. Reduce heat to medium-low, and let simmer for 10-15 minutes to reduce until it is thickens slightly and makes a syrup. Remove from heat and strain through a fine-mesh strainer if desired. Refrigerate.
Whisk together 1/4 cup blueberry syrup with 1 cup cold milk to serve.
This recipe will also work with strawberries, blackberries, lingonberries, and cherries.