In a medium bowl, whisk together the soy sauce, apple juice, water, vinegar, brown sugar, ginger, garlic, and black pepper. Set aside.
Heat 1 tablespoon olive oil in a large skillet over medium-high heat.
Add the chicken to the skillet, stirring occasionally until browned and cooked through, 7-8 minutes.
Add in the soy sauce mixture, and stir to combine.
Turn the heat down to medium-low and simmer for 15 minutes, until the liquid has reduced by about half.
In a small bowl mix the cornstarch with 3 tablespoons of cold water until smooth.
Add this into the chicken and stir to combine. Cook for 1 minute, as the mixture will thicken quickly.
Remove the pan from the heat and serve over rice. Top with green onions if desired.
