In a large saucepan, combine chicken broth, orange juice, sugar, vinegar, soy sauce, sriracha , ginger, garlic, lemon juice, orange zest and red pepper flakes. Place pan over medium high heat, bring sauce to a boil and simmer for a few minutes - about 3-4 minutes.
In a small bowl, whisk together water and cornstarch to form a paste. Slowly stir cornstarch mixture into orange sauce. Continue cooking until sauce begins to thicken, about 5 minutes. Remove sauce pan from heat and set aside.
Season chicken cubes with salt and pepper to taste. In a medium-sized shallow dish, whisk together cornstarch and flour, set aside. In a small shallow dish, whisk eggs. Dip chicken into egg mixture and then dredge in the cornstarch mixture. Place on a plate and set aside.
Meanwhile, heat 2-3 inches of oil in a heavy bottom pot or wok over medium high heat. Working in small batches, fry chicken pieces stirring often until cooked through and golden brown - about 3 to 4 minutes. Remove from oil and drain on a paper towel lined plate. Repeat the process for the remaining chicken cubes.
Toss fried chicken pieces together with orange sauce, garnish with green onions and serve immediately with rice.