Sprinkle both sides of the chicken breasts with onion powder, salt, and pepper.
Heat oil in a large skillet over medium-high heat. Add chicken and cook until golden brown, about 5 minutes per side.
Add garlic and mushrooms and cook until mushrooms have released their liquid and are reduced in size, about 5 minutes.
Stir together water, white wine, and gravy packet in a small bowl and pour into the skillet.
Bring liquid to a simmer, cover, reduce heat to medium, and cook for 5 minutes. Turn chicken breasts and continue cooking until chicken is no longer pink in the center and the juices run clear, about 5 more minutes. An instant-read thermometer inserted into the center should read at least 165 degrees F (74 degrees C).