Add vodka, sweet potato syrup, and lemon juice to a shaker filled with ice. Shake well for 10–15 seconds.
Strain into a Collins glass filled with fresh ice.
Top with club soda and stir gently.
Garnish with a sweet potato slice or lemon wheel.
Notes
To make sweet potato syrup: Simmer 1 cup water, 1 cup sugar, 1/2 cup cooked mashed sweet potato, and pinch of cinnamon until syrupy. Strain and cool. For a richer drink, add a dash of bitters or orange liqueur.