In a medium bowl, whisk together apple cider vinegar, olive oil, sugar, salt, and pepper to taste. Stir in mint and parsley until well combined.

Slice cucumbers into half-moons, thinly slice red onion, and cut tomatoes into wedges.

In a large shallow dish, place all prepared vegetables and pour the dressing over them. Gently toss to coat.

Cover with plastic wrap and refrigerate for at least 30 minutes to marinate.

After marinating, give the salad a gentle toss before serving chilled.