Slice the cucumbers into medium, even slices, about ¼ inch thick. Slice the onion into thin half-rings.

Transfer the sliced cucumbers and onions into a half-gallon jar or leak-proof container.

In a mixing bowl, combine white vinegar, sugar, salt, celery seed, and minced garlic if using. Stir until fully dissolved.

Pour the brine mixture into a saucepan and heat over medium heat until almost boiling, stirring occasionally.

Let the heated brine cool to room temperature for about 15-20 minutes.

Carefully pour the cooled brine over the cucumber and onion slices in the jar, ensuring they are fully submerged.

Seal the jar with its lid and refrigerate for at least 24 hours; for best results, let them marinate for 2-3 days.

After the waiting period, your homemade no-cook refrigerator pickles are ready to be enjoyed!