Wash the cucumbers and slice them thinly, about 1/8-inch thick. If using regular cucumbers, consider peeling them for a softer texture. Place the cucumber slices in a large bowl.

Using a sharp knife, slice the sweet onion thinly and add it to the bowl with the cucumbers.

In a separate mixing bowl, whisk together the apple cider vinegar, granulated sugar, salt, and pepper until the sugar dissolves completely.

Pour the dressing over the cucumber and onion, tossing gently to ensure all the vegetables are covered.

Let the salad sit for at least 30 minutes in the refrigerator to allow the flavors to meld together. It can also be made a day in advance for even better flavor.