Preheat oven to 400° F. Line 2 baking sheets with parchment paper.
Wash and dry the fresh green beans, set aside.
Beat the egg in a shallow dish with the water. In another shallow dish, stir together the Parmesan, garlic powder, onion powder and some salt and pepper. Dip the green beans in the egg mixture, making sure to fully coat them. Using a fork, gently transfer the green beans to the cheese mixture and roll to evenly coat on all sides with the Parmesan cheese mixture.
Transfer the green beans to the prepared baking sheets, making sure the beans are evenly placed in a single layer and not touching. Bake until golden brown and crisp-tender, about 10 minutes.
*You can squeeze a little lemon juice over the top, if desired.