In a large bowl, combine flour, cornstarch, salt and pepper. Whisk in egg, sparkling water and sesame oil until smooth. Add chicken pieces; toss to evenly coat. Cover; transfer to the refrigerator. Let chicken marinate at least 30 minutes.
Heat oil about 1/2 to 1 in. deep in a large wok or Dutch oven to 350°. Working in batches, add a few pieces of the battered chicken to the preheated oil. Cook, turning occasionally until the chicken is deeply golden brown on all sides and cooked through, about 5-6 minutes. Transfer fried chicken pieces to a paper towel-lined sheet pan to drain. Repeat with remaining chicken pieces.
Heat canola oil in a large skillet to medium-high heat. Add red pepper flakes, garlic and ginger; cook 30-60 seconds or until fragrant. Add sugar, brown sugar, rice vinegar, orange juice, soy sauce and orange zest; stir until sugars dissolved and mixture begins to bubble.
In a small bowl, whisk together water and cornstarch until dissolved. Add to sauce; stir until smooth. Cook sauce until it thickens, 1-2 minutes.
Add fried chicken pieces to sauce; toss gently to coat. Serve with cooked rice and top with green onions and sesame seeds.