Place the flour in a shallow bowl or plate. In a separate bowl, whisk together the egg and 1 tablespoon water. In another shallow bowl or plate, combine the panko, cilantro, salt and pepper.
Begin by coating the mozzarella sticks in batches of 2, first dredging in the flour mixture and shaking off excess. Then dip in the egg mixture, letting any excess drip off. Finish by dredging in the panko crumb mixture and shaking any off excess. Transfer the breaded cheese sticks to a sheet pan greased with nonstick cooking spray. Cover and freeze until frozen, about 4 hours and up to 2 days (this will lessen the oozing of the cheese).
Preheat the oven to 400 degrees F.
Lightly spray the cheese sticks with nonstick cooking spray. Bake until the cheese is soft and the sticks are lightly browned, about 12 minutes.