Begin by slicing your jalapeños into rings. If you prefer less heat, remove the seeds.

In a saucepan, combine the sugar, white vinegar, water, salt, and mustard seeds.

Heat the mixture over medium heat, stirring until the sugar and salt dissolve to create a brine.

Remove the brine from heat and add the sliced onions and minced garlic. Stir to combine.

In a clean jar, carefully layer the sliced jalapeños, making sure to pack them tightly.

Using a ladle, pour the prepared brine over the jalapeños in the jar, ensuring all jalapeño rings are submerged.

Allow the jar to cool to room temperature before sealing it with a lid.

Place it in the refrigerator and let the flavors meld for at least 24 hours before using.