In a cocktail shaker, add the fresh blackberries along with the thyme leaves. Use a muddler or the back of a spoon to gently crush the blackberries and thyme until the blackberries are juicy and aromatic.
Incorporate the honey or agave syrup and the freshly squeezed lemon juice into the shaker. Muddle the mixture again for about 30 seconds, allowing the flavors to meld beautifully.
Fill the shaker with ice cubes to chill the mixture and pour in the chilled sparkling water. Secure the lid tightly and shake the shaker gently to combine the ingredients without losing the carbonation.
Strain the blackberry-thyme concoction into a tall glass filled with ice, ensuring that any solids are left behind for a smooth drink.
Garnish your mocktail with fresh thyme sprigs and a few whole blackberries for an appealing presentation.
Notes
Adjust sweetness to taste with honey or agave syrup.