Wash and trim the Brussels sprouts. Split in half. You can quarter them if they are large.
Place the Brussels sprouts in a steamer basket. Pour the water into the inner pot, and place the trivet inside. Place the basket on the trivet. Lock the lid into place. Select Steam, and set the time to 1 minute.
After cooking, Quick Release the pressure. Unlock and remove the lid. Using tongs, carefully transfer the Brussels sprouts to a serving plate. Discard the water, and wipe the inner pot dry.
Select Sauté, and pour in the oil. Once hot, add the garlic and sauté for 1 minute. Add the Brussels sprouts, vinegar, salt, and pepper, and sauté for 2 minutes.