Mix equal parts salt and chili powder on a small plate for the rim (if using).
Run a lime wedge around the rim of the glass and dip in the salt mixture.
Add jalapeno slices to the shaker and muddle gently 2-3 times.
Pour in tequila, lime juice, and sweetener.
Fill the shaker with ice and shake vigorously for 15 seconds.
Strain the mixture into the prepared glass filled with fresh ice.
Top with sparkling water and stir once.
Garnish with lime wheel and jalapeno slice.
Notes
Adjust the spice level by using more or fewer jalapeno slices. For less heat, remove the seeds.Fresh lime juice makes a big difference - avoid bottled juice.Store leftover jalapeno slices in an airtight container in the fridge for up to 3 days.The drink contains 145 calories when made with silver tequila and zero-calorie sweetener.Make it sweeter by adding more sweetener to taste.