Combine sugar, water and sliced jalapeño in a small saucepan over medium heat. Stir until the sugar dissolves and simmer for 10 minutes. Remove from heat and let steep for about 30 minutes. Strain into a jar or other container with a lid.
Spicy Peach Margarita
Combine tequila, lime juice, jalapeño simple syrup and peaches in a blender. Add about 1 ½ cups of ice if using frozen peaches (3 cups of ice if using fresh) and blend until smooth. Pour into glasses and serve!
Notes
If you'd like to rim the glass, you can use salt or my preference is a chile sugar rim. Combine 2 tablespoon sugar with 1 teaspoon chile powder and rub the rim of the glass with a lime wedge. Dip the glass into the sugar mixture to coat the rim.
If you would like the margarita to be spicier, add a few slices of fresh jalapeño to the blender.