Fill a cocktail shaker with ice. Add vodka, lavender simple syrup, and lemonade.
Shake well for 15-20 seconds until the mixture is very cold.
To make lavender simple syrup: Combine water and sugar in a small saucepan. Heat until sugar dissolves. Add dried lavender and simmer for 5 minutes. Remove from heat and let steep for 30 minutes. Strain and cool completely.
Strain the cocktail into a Collins glass filled with fresh ice.
Garnish with a fresh lavender sprig.
Notes
The lavender simple syrup can be stored in an airtight container in the refrigerator for up to 2 weeks.For a mocktail version, skip the vodka and add extra lemonade or sparkling water.Fresh lemon juice makes better lemonade than store-bought options.Don't over-steep the lavender syrup or it may become bitter.