Spray inside of 1 1/2 or 2-quart slow cooker with cooking spray. Combine sauce and water in slow cooker, then drop in meatballs. Cook on low 5-7 hours. Break spaghetti into fourths and stir into meatball and sauce mixture. Cook on high for 1 hour, stirring occasionally.
Serve with garlic bread and a side salad - yum! :).