Drain the sardines and place them in a bowl. Gently break into bite-sized pieces with a fork.
In a large salad bowl, arrange the mixed greens as a base.
Add the halved cherry tomatoes, sliced red onion, and diced cucumber.
If using, add the Kalamata olives, capers, feta cheese, and fresh herbs.
In a small bowl, whisk together the lemon juice, olive oil, and minced garlic (if using).
Add the sardine pieces to the salad.
Drizzle the dressing over the salad ingredients.
Season with salt and freshly ground black pepper to taste.
Gently toss all ingredients until everything is lightly coated with the dressing.
Serve immediately for the freshest flavor and best texture.