Lightly grease the inner pot of your Instant Pot. Turn on "Saute" mode. Add sausage. Crumble it apart with a wooden spoon as it cooks.
Once sausage is cooked and crumbled, turn Instant Pot off. Add grits, water, half-and-half, salt, and garlic powder. Give everything a stir. Place lid on pot and make sure valve is in "Sealing" position.
Turn Instant Pot on "Pressure Cook" for 10 minutes. Let it release pressure naturally for 15 minutes and then open the valve to release remaining pressure. Carefully remove lid.
Stir in butter, cheese, and pepper. Check for seasoning and add more salt if desired.