1. In a saucepan, bring the water and sugar to a boil, stirring until the sugar has completely dissolved.
2. Add the thyme, reduce the heat, and simmer for 5 minutes.
3. Remove from the heat and let steep for 10 minutes.
4. Remove the thyme sprigs, then add the frozen raspberries and the raspberry white balsamic vinegar.
5. Using an immersion blender, blend until smooth. Strain through a fine-mesh sieve if desired.

To Serve

1. Fill a glass with ice.
2. Pour in about one-third shrub, then top with sparkling water.
3. Stir gently and serve chilled.