Whisk together orange juice, soy sauce, sugar, rice vinegar, ginger, and garlic in a small bowl until the sugar dissolves, then set aside.
Toss the chicken pieces in cornstarch until evenly coated, shaking off any excess.
Heat vegetable oil in a large skillet over medium-high heat, then fry the chicken in batches for 3 to 4 minutes per side until golden and crispy, reaching 165°F / 74°C internally.
Remove the chicken and drain on paper towels, then pour out excess oil and return the skillet to medium heat.
Pour the orange sauce into the skillet and simmer for 2 to 3 minutes until thickened and glossy.
Add the crispy chicken back to the skillet and toss quickly in the sauce for 30 seconds to coat evenly.
Serve immediately over rice to keep the coating crisp.