Preheat the oven to 325°F. Lightly grease a 9x13-inch baking dish and set it aside.
Cut the chicken into bite-sized pieces, about 1 to 1½ inches. Season the chicken with salt and pepper.
Add the cornstarch to a shallow bowl or dish. Add the chicken pieces and toss until each piece is well coated.
In a separate bowl, whisk the eggs until smooth.
Working with a few pieces at a time, dip the cornstarch-coated chicken into the beaten eggs, letting any excess drip off.
Heat about ¼ inch of vegetable oil in a large skillet over medium heat. When the oil is hot, add the chicken in batches, being careful not to crowd the pan.
Brown the chicken for 1 to 2 minutes per side, just until golden. The chicken does not need to be fully cooked at this point because it will finish baking in the oven.
Transfer the browned chicken pieces to the prepared baking dish and spread them into an even layer.
In a small bowl, whisk together the sugar, ketchup, apple cider vinegar, hoisin sauce, soy sauce, and crushed garlic until combined.
Pour the sauce evenly over the chicken. Gently toss or stir so the chicken is coated in the sauce.
Bake uncovered for 1 hour, stirring every 15 to 20 minutes so the sauce coats the chicken and thickens evenly.
Serve hot over rice.