Cut each chicken breast into cubes. In a large, nonstick frying pan, heat the olive oil over medium heat. Add the chicken and cook until golden brown, about 10 minutes. In a large serving bowl, combine the cooked chicken, pineapple chunks, broccoli, spinach and onions.

To make the dressing, whisk together the olive oil, vinegar, reserved pineapple juice, sugar and cinnamon in a small bowl. Pour over the salad. Toss gently to coat evenly. Serve immediately.