If you want "premade something" and are okay with eating breakfast in your room, you can see what's on the shelf in the grocery area in the gift shop in Jambo House. I haven't been recently, but pre-COVID the gift shops in the DVC resorts had Entenmann's products - you could get a box of donuts, mini muffins, cinnamon buns. You also could get bagels, cereal, and poptarts.
You also can look at the grab & go items in the Mara and see if there's something you want to keep in your room to eat the next day. Allears.net shows hard boiled eggs, yogurt and fruit as well as bakery items (cinnamon roll, Danish, croissants, muffin, banana nut bread). I'm not sure how late in the day the bakery items are available if you want to get one for the next day.
