Put water and sweet potatoes in the Instant Pot. Close the lid, turn the valve to a Sealing position and press the "Pressure Cook" or "Manual" button and set the time to 30 minutes on High pressure.

When it's done cooking, quick release (QR) the steam. Remove sweet potatoes from the pot, drain the water, peel the sweet potatoes and put them back in the pot. Mash sweet potatoes with a potato masher and mix in the maple syrup, cinnamon and butter (if using).