Combine gluten-free flour, cornstarch, and ground ginger in a large plastic storage bag.
Cut chicken breasts into 1-inch pieces. Whisk eggs in a medium bowl, add chicken, and coat evenly.
Place chicken in the flour mixture bag, seal, and shake until well coated. Refrigerate while heating oil.
Heat oil in a skillet to 350°F. Fry chicken pieces for 3–4 minutes until light golden brown, working in batches.
Drain on a paper towel-lined plate. Carefully pour out oil and wipe skillet clean.
To make the sauce: In the same skillet, combine sugars, garlic powder, and ginger. Stir in orange juice, soy sauce, and rice vinegar.
Whisk cornstarch and water together in a small bowl, then stir the slurry into the sauce. Cook until thickened to a maple syrup-like consistency.
Return fried chicken to skillet and toss until evenly coated with the sauce. Serve hot over rice.