Toss the soy sauce and chicken in a large bowl, and cover. Let marinate for 5 to 10 minutes while you prepare the other ingredients.
In a medium-sized bowl, whisk together the pineapple juice, ketchup, rice vinegar, oyster sauce, sugar, cornstarch, and sriracha. Set aside.
In a large bowl, whisk together the flour, salt, and pepper. Divide the flour mixture evenly into two bowls.
Remove the chicken from the soy sauce marinade and lightly pat dry with paper towels. Toss the chicken pieces in one of the flour mixture bowls, completely coating the chicken. This is your chicken’s first coating of flour.
Next, arrange an assembly line for dredging your chicken. Dip each flour-coated piece of chicken into the whisked egg, then dip it into the second bowl of flour mixture, and place the coated chicken on a plate. Repeat until all the chicken pieces are dredged.
In a large wok or a skillet, heat oil over medium heat. Once the oil is heated and shimmering, add the chicken. Fry the chicken on all sides, tossing and stirring occasionally for about 5 to 7 minutes, or until crispy, golden brown, and cooked through.
Decrease the heat to medium-low. Add the previously prepared pineapple juice mixture and the chicken pieces to the skillet; stir until the chicken pieces are evenly coated. Stir occasionally until the sauce has thickened, another 1 to 2 minutes.
Remove from heat, and garnish with sesame seeds and chopped green onions. Serve immediately.