Put water and sliced mushrooms in the Instant Pot. Close the lid and turn the valve to a Sealing position. Press the "Pressure Cook" or "Manual" button and set the time to 6 minutes.
When the Instant Pot finishes cooking, quick release (QR) the steam.
Drain the mushrooms and return them to the Instant Pot.
Add olive oil and minced garlic to the mushrooms and mix.
Press the "Saute" button on the Instant Pot and set the time to 5 minutes. Saute the mushrooms, stirring every 30 seconds, until fragrant (about 2 minutes).