Spray a small nonstick skillet with cooking spray and heat over medium-high.
In a small bowl, whisk 1 egg, 1 egg white, 1 tablespoon milk, and a dash of salt and pepper. Pour into skillet and tilt to coat bottom. Push eggs toward center as they cook, tilting skillet and allowing runny part to coat bottom again. Continue for 1-2 minutes or until eggs are just set but top still appears wet.
Add 1/4 cup cheese and 1/2 cup spinach to center of omelet and fold one side over the other; transfer to plate. Continue until 4 omelets have been cooked.
Toast bread and spread with butter. Slice kiwis. Serve omelets with toast and kiwis.