In a glass bowl, lightly mash the blueberries with the sugar and torn basil leaves.
Cover and refrigerate for 8 to 24 hours, until the berries release plenty of juice.
Strain through mesh strainer into mason jar.
Stir in the apple cider vinegar and shake well to mix.
Refrigerate another 12 to 24 hours so the flavors can mingle.
Strain through a fine mesh strainer into a clean bottle or jar, pressing gently on the solids.
To serve, add 1 to 2 tablespoons of the shrub to a glass of ice and top with water or sparkling water. Add lemon if you like a brighter finish.