Slice the Fresno chiles into thin rings after removing the seeds.
Set them aside while preparing the brine.
Combine water, rice wine vinegar, sugar, and kosher salt in a small saucepan.
If desired, add a bay leaf and garlic.
Bring the mixture to a simmer, stirring until the sugar and salt dissolve completely.
Ensure the heat is medium-high.
Carefully pour the hot brine into a heatproof jar, then add the sliced chiles.
Make sure the chiles are fully submerged.
Allow the mixture to cool completely before sealing the jar.
Store in the refrigerator to enhance the flavors.