Add all ingredients into a shaker with ice and shake briefly.
Strain into a Collins glass over fresh ice.
Top with the soda water.
Garnish with orange and lemon peels cut into lightning bolts.
*Lavender-lychee syrup: Drain syrup from 16 oz can of lychees. Bring syrup to a boil over medium heat and add 5 g dried lavender. Remove from heat and steep 10 minutes. Strain solids, add 5 oz granulated sugar and stir to combine. Refrigerate and store. Will last 4 weeks in refrigerator.