Lightly spray large skillet with nonstick cooking spray. Heat over medium-high heat. Cook broccoli and water 4-5 minutes, or until broccoli is tender. Remove from heat. Transfer broccoli to dish. Using paper towels, wipe skillet clean.
In large bowl, whisk egg whites, milk and pepper until combined.
Lightly spray skillet with cooking spray. Heat over medium-high heat. Pour in egg white mixture. Cook 2-3 minutes, or until almost firm, stirring constantly with spatula. Stir in broccoli and cheddar cheese. Remove from heat.
Just before serving, split and toast English muffins. Transfer to plates. Spoon egg mixture onto muffins.