Make the Jalapeño Simple Syrup (up to a week ahead)
In a saucepan, bring the sliced jalapeños, water, and sugar to a boil. Stir the mixture while it's heating to dissolve the sugar crystals. When it comes to a boil, turn the stove off and leave the syrup to cool completely- on or off the stove- for at least 10 minutes.
After the simple syrup has had time to steep and has cooled completely, pour it into a jar through a small sieve. Discard the jalapeño slices and seeds.
Store the simple syrup in a jar or bottle that has a tight-fitting lid. It's best kept in the fridge for up to a week.
Make the Pineapple Jalapeño Margarita
Fill a cocktail shaker halfway with ice. Pour the canned pineapple juice into the shaker.Add 1-2 tablespoons of the cooled jalapeño simple syrup to the cocktail shaker, or to taste. The more syrup you use, the spicier and sweeter the margarita will be.
Add the tequila to the cocktail shaker. Cap the shaker and shake vigorously. When the cocktail shaker frosts over, it's chilled enough to pour.
Strain the pineapple jalapeño margarita cocktail into cocktail glasses. Garnish as desired and enjoy responsibly.
Notes
Pitcher Pineapple Jalapeño Margaritas (serves 4): 4 cups ice 2 1/2 cups pineapple juice 1/2-1 cup jalapeño simple syrup 1 cup tequila blanco
combine and mix as above.
Virgin Pineapple Jalapeño Margaritas: 1 cup ice 1 1/2 cups pineapple juice 1-2 tablespoons jalapeño simple syrup