Make and cool the brine. Combine the vinegar, kosher salt, and sugar in a small saucepan. Bring to a boil over high heat, stirring to dissolve the salt and sugar. Remove from heat and add the cold water. Stir to combine, cover the saucepan, and place it in the refrigerator to cool.
Prep the veggies. Slice the cucumbers into rounds, spears, or halves while the brine is chilling. Smash the garlic cloves in half, but do not mince or chop.
Pack the jars. Place 8 sprigs of fresh dill and 1 tablespoon of peppercorns into each of the two clean quart jars. Then, pack the cucumber slices tightly into the jars. Add a pinch of red pepper flakes to each jar if you want a hint of spice.
Pour the brine. After the brine has cooled down, pour it over the cucumbers in the jars, making sure that they are completely covered.
Chill and store. Cover the jars with lids and put them in the fridge. Let the pickles chill for at least a day before eating to let the flavors develop. The pickles will stay good in the fridge for up to 2 months.