4 sprigs fresh mint, divided
2 teaspoons white sugar
3 fluid ounces passion fruit-flavored rum
1 lime, juiced
3 fluid ounces unsweetened guava nectar
2 fluid ounces club soda, or as needed (optional)
Fill a glass with ice.
Muddle 3 sprigs mint and sugar together in a cocktail shaker; add ice, rum, lime juice, and guava nectar. Cover and shake 10 times. Strain drink into glass filled with ice; add club soda and garnish with 1 mint sprig.