Heat oil in a large skillet over medium heat.
Add cubed chicken and cook, stirring, for 7-8 minutes, until no longer pink, browned, and a little crisped.
Meanwhile, make teriyaki sauce: Combine water, soy sauce, honey, pineapple juice, brown sugar, garlic, and ginger in a medium saucepan over medium heat.
Whisk cornstarch-water mixture until dissolved and add to the sauce.
Cook, stirring occasionally, for about 5 minutes, until sauce thickens. If the sauce becomes too thick, add more water to thin it out.
Add sauce to the skillet with the chicken and cook for about 5 minutes to thoroughly coat chicken.