1. In a medium bowl combine eggs, egg whites, Canadian bacon, the water, green onion, and salt. Beat with a wire whisk or rotary beater until well mixed.
2. Lightly coat an unheated large nonstick skillet with nonstick cooking spray. Preheat over medium heat. Add egg mixture to skillet. Cook, without stirring, until mixture begins to set on the bottom and around edge. Using a spatula or a large spoon, lift and fold the partially cooked eggs so that the uncooked portion flows underneath. Continue cooking about 2 minutes more or until egg mixture is cooked through but is still glossy and moist. Remove from heat immediately.
3. Fill pita halves with egg mixture. If desired, sprinkle with cheese.