Cut each chicken breast half lengthwise. Mix egg white and water in a medium glass or plastic bowl. Add chicken; turn to coat both sides and let stand 10 minutes.
Heat oven to 450 degrees. Spray nonstick cookie sheet with cooking spray. Remove chicken from egg mixture; discard egg mixture. Mix flour, baking soda and red pepper in a large resealable plastic bag. Add 1 chicken piece at a time. Seal bag; shake to coat chicken. Place chicken on cookie sheet; spray with cooking spray about 5 seconds or until surface of chicken appears moist.
Bake uncovered for 20 to 25 minutes or until juice of chicken is no longer pink when centers of thickest pieces are cut. While chicken is baking, prepare Chinese Lemon Sauce. Let chicken stand 5 minutes;slice each piece into 5 slices. Pour sacue over chicken. Garnish with lemon slices and green onion.
Chinese Lemon Sauce: Heat all ingredients except cornstarch and cold water to boiling in 1-quart suacepan, stirring occasionally. Mix cornstarch and cold water; stir into sauce. Cook and stir about 30 seconds or until thickened. Serve warm, or cover and refrigerate up to 2 weeks.