Place the cucumbers in a 1-quart jar or some other container with a tight-fitting lid.
In a bowl, combine the vinegar, onion, garlic, sugar, dill seed, peppercorns, bay leaf, 2 teaspoons salt, and ¾ cup hot tap water. Stir until the sugar dissolves.
Pour the vinegar mixture into the jar with the cucumbers, cover, and refrigerate for at least 1 day before serving. The pickles will last up to 1 week.