In a large bowl, combine chicken pieces with water, baking soda, and salt; mix vigorously until liquid is mostly absorbed by the chicken.
Add eggs to the chicken mixture and stir until fully incorporated; then pour in cornstarch and mix thoroughly until no dry bits remain; finish by stirring in the oil evenly.
Pour 2 to 3 inches of oil into a wok or deep pan and heat until it reaches 375°F.
While the oil warms, prepare the sauce by mixing orange juice, orange zest, ketchup, sugar, vinegar, and cornstarch in a bowl; set aside.
Carefully add chicken pieces in a single layer to the hot oil, frying in batches if necessary; cook for 4 to 5 minutes, stirring occasionally to keep pieces separate.
Remove chicken from oil and drain on paper towels or a rack for 2 to 3 minutes.
Reheat the oil to 375°F, then return chicken to oil for a second frying; cook for another 5 to 6 minutes until chicken turns golden and crisp.
Drain the fried chicken once more and set aside.
Heat a small amount of oil in a wok or large skillet over medium heat; add the white portions of green onion, minced garlic, and chili flakes or whole dry chili if using; stir fry until aromatic, about 10 to 15 seconds.
Give the sauce mix a good stir, then pour it into the wok; raise heat to medium-high and cook sauce until it thickens and becomes glossy, stirring frequently.
Add the crispy chicken to the sauce, tossing well to coat each piece evenly in the vibrant orange glaze.
Serve right away, garnished with the green parts of the green onion, alongside white or fried rice. Enjoy!