Score cucumbers with a fork and cut into slices. Place them in a deep jar with the garlic and chill overnight. Combine the vinegar, water, sugar, and salt in a saucepan and bring to a boil. Remove from the heat immediately and chill it over an ice bath. Pour the dressing over the cucumbers and season with pepper and parsley. Chill covered overnight. Serve in a decorative bowl; garnish with red onion rings.