To make the jalapeño simple syrup: In a small saucepan, combine the sliced jalapeños, sugar and water. Bring to a boil over medium-high heat, then reduce to a simmer. Cook for 10 minutes, then remove the pot from the heat. Steep for 10 minutes. 

Strain the syrup into a mason jar or heatproof container with a lid. Note: leftover jalapeño simple syrup can be stored in the refrigerator for up to 7 days. 

To make one Sumo mocktail: Fill a cocktail shaker halfway with ice. Add the Sumo juice, guava juice, ¾ ounce jalapeño simple syrup and lime juice. Shake for 15 seconds or until chilled through. 

Fill a lowball glass with crushed ice and strain the mocktail into the glass. Top with sparkling water and garnish with the mint sprig.