Soak the bread slices in water for 3 minutes.
Break the soaked bread into small pieces.
In a large bowl, beat the egg and add in the soaked bread pieces, breadcrumbs, parmesan cheese, water, parsley, olive oil, garlic powder, Italian seasoning, black pepper, and red pepper flakes. Stir to combine.
Add the ground meat and mix.
Shape the mixture into balls.
Set to Saute mode on High. Once hot, add the oil. Brown the meatballs on each side, about 4 to 5 minutes. Turn the pressure cooker off.
Remove the meatballs and wipe the grease off the Instant Pot.
Pour half of the spaghetti sauce into the pot and arrange the meatballs on top of it in a single layer.
Break the spaghetti noodles in half, then lay them on top of the meatballs in different directions.
Pour the remaining sauce over the noodles.
Fill half of the empty sauce jar with water. Shake, then pour on top of the noodles, making sure the noodles are completely covered. Do not stir.
Secure the lid. Set the valve to Sealing.
Set to Manual and cook on High for 7 minutes.
Once the timer is done, do a quick release. Remove the lid and gently stir the pasta and meatballs together in the sauce. Serve with parmesan cheese on top!