Mix together the chicken broth, juice, sugar, vinegar, soy sauce, garlic, sriracha, ginger and pepper in a bowl to make marinade.
Pour slightly more than 1/2 of the marinade into ziploc bag. Set the rest aside to make sauce later. Slice chicken into 1 inch cubes.
Add chicken into marinade bag.
Let chicken marinade for at least 2 hours.
Pour oil into frying pan at least 1 inch deep and heat to medium heat. In a small bowl, whisk egg. In a separate small bowl, pour 1 cup cornstarch.
Drain chicken from marinade. Dunk chicken first in egg, then coat in cornstarch and then put into heated frying pan. Fry for a few minutes until chicken is a light golden brown. You can do a few pieces at a time, in small batches until all chicken is used up.
Place already fried chicken aside on plate lined with paper towel.
In a small saucepan, pour the remaining marinade that was previously set aside.
Add in 2 tbsp of cornstarch and mix so it is completely dissolved. Cook on low heat, stirring constantly so that the cornstarch does not get chunky. Cook for a few minutes until sauce becomes thick.
Set aside about 1/3 of the sauce. Leave remaining 2/3 in saucepan and add in fried chicken pieces and coat with sauce.