Add sliced strawberries and sugar to a mixing bowl. Stir until the strawberries are evenly coated.
Cover the bowl and let the strawberries rest until they release their natural juices and become softer.
Gently crush the basil leaves to release their aroma, then add them to the strawberry mixture.
Allow the basil to infuse briefly with the strawberry syrup. Remove the basil once the desired herbal flavor develops.
Strain the strawberry mixture through a fine mesh strainer, pressing gently to extract the liquid.
Mix the strawberry syrup with vinegar until fully combined.
Taste the shrub and adjust the balance if needed by adding more sweetness or acidity.
Transfer the finished shrub syrup into a clean glass jar and refrigerate until ready to use.