Add the sliced banana peppers and minced garlic evenly Into two 1-quart mason jars (or 4 1-pint jars).
In a saucepan over medium heat, combine the white vinegar, water, kosher salt, sugar, mustard seeds (optional), and celery seed (optional). Stir until the mix is completely dissolved and nearing boil, then remove from heat and allow the brine to cool to room temperature.
Add the brine to the mason jars, leaving 1/2 inch free at the top of each jar, then seal with a lid.
For best flavor, allow the banana peppers to pickle for a minimum of 24 hours or - even better - up to a week prior to eating.