Preheat oven to 400°F/200°C. Line two 9x13 pans with foil and spray with cooking spray.
Stir ground beef, stuffing mix, eggs, onion and water together, just until blended. Shape into meatballs, each about 1 inch in diameter. Plan on making around 65 meatballs, depending on size. Place them in the prepared pans.
Bake 20 minutes, or until done (160ºF/71°C).
Mix gravy and sour cream in large saucepan or skillet. Add meatballs; gently stir to coat. Cook on low heat 5 minutes, or until sauce is heated through, stirring occasionally. Thin sauce with water, if needed.
Bake the meatballs for 10 minutes at 350°F/175°C. Remove from the oven and let cool. Place in gallon size resealable freezer storage bag. Mix the gravy and sour cream and place in sandwich size bag then place with the meatballs inside the gallon size bag and freeze.
To PREPARE after freezing:
Thaw meatballs and sauce. Cook meatballs at 350°F/175°C for 15 minutes, or until cooked through. Then heat in the sauce as directed above.