Set Instant Pot to saute. Add the ground beef, sausage, garlic and onion and cook until meat is no longer pink; drain, if needed.
Add the tomatoes, marinara sauce, tomato paste, Italian seasoning, fennel seed, bay leaves, sugar, salt and pepper to the pot; mix well. Deglaze the pot (remove bits from the bottom with a spoon).
Place the cover on the pot and set timer to 10 minutes on high pressure (pressure cook setting). It will take the IP around 10 minutes to build up pressure before it begins cooking.
When cooking is done, let the pressure release naturally for 10 minutes; do a quick release.
Remove cover, stir and remove/discard bay leaves. Serve with your favorite pasta and top with Parmesan cheese, if desired. Store leftovers in a sealed container in the fridge!