In a small saucepan, combine vinegar, salt, and sugar over high heat. Whisk together until the salt and sugar are dissolved. Transfer to a bowl and whisk in the cold water.
As the vinegar solution is cooling, slice the ends off the cucumbers, then slice each cucumber into quarters to create long spears. Alternately, slice into rounds instead if desired.
Pack cucumbers into a 1 quart wide-mouth mason jars. Divide evenly the garlic, mustard seeds, black peppercorns, red pepper flakes, and chopped dill, and add to the jars.
Add cooled brine to the jars, making sure to cover the cucumbers completely. A wide-mouth funnel may be helpful for this step. If there is not enough brine to cover the cucumbers, add cold water to each jar until they are completely submerged.
Cover jars and refrigerate for at least 24 hours. Enjoy! The pickles will stay good in the refrigerator for 2-4 weeks.