Peel and thinly slice the onions. Rinse the tomatoes, and cut into wedges. Rimse the cucumber and slice. Drain and dice the feta cheese. Drain the olives, then combine all the prepared ingredients in a bowl.
For the salad dressing, peel and chop the garlic cloves. Mix with the olive oil and sugar, then stir in the lemon juice. Season with salt and pepper. Mix into the salad, and combine thoroughly. Serve the salad on plates.