In a saucepan, combine 160 g sugar, 160 ml water, and 125 g blueberries. Heat on high until boiling, then reduce to medium heat. Simmer for 5 minutes, stirring frequently.
Strain through a pasta sieve and cool the syrup for 2 hours. (Optional: save the solids for blueberry jam. To scale for multiple servings, increase the ingredients proportionally.)
Squeeze 2 lemons and strain the juice into 300 ml of the cooled syrup.
In a container or bottle, combine 500 ml water, 300 ml lemon-blueberry syrup, and 200 ml vodka. Stir well.
Pour into a glass, add several ice cubes, and serve.