Slice cucumbers and discard ends. Place the cucumbers into a quart jar (or two pint jars) along with the crushed garlic, peppercorns, and mustard seeds. Tuck the fresh dill into the sides of the jar.
1 pound seedless cucumbers, 2 cloves garlic, 1 teaspoon black peppercorns, ½ teaspoon mustard seed, 2-3 sprigs fresh dill
In a bowl or liquid measuring cup, combine the vinegar, water, salt, and sugar. Whisk until the salt and sugar are completely dissolved.
1 cup distilled white vinegar, 1 cup water, 1 tablespoon pickling salt, 2 teaspoons granulated sugar
Pour the brine over the cucumbers slowly, letting it fill in the cracks between the cucumbers. You should be able to use all of the brine.
Cover tightly and place in the refrigerator. Let rest for at least 24 hours before eating, but preferably longer for better pickle flavor.