Peel and cube the potatoes into 1” pieces. You can make them larger than this, if you like, but the cook time will vary based on the size of the cubes.
Pour the water into the inner pot. Put the sweet potatoes into a steamer basket and set it into the Instant Pot. If your steamer basket does not have legs to elevate it out of the water, place the trivet into the pot first. You don't want the potatoes resting in water, or they will become mushy.
Lock on the lid and set the valve to sealing. Press the Manual or Pressure Cook button and set the time to 3 minutes on high pressure. It will take approximately 5-8 minutes to build up pressure.
When the cook time is up, release the pressure manually. Don't let it sit for too long before releasing pressure or the potatoes might over cook. Open the lid and take out the steamer basket to cool outside of the pot.
Notes
3 minutes for 1" cubes produces a soft potato with a little bit of bite and structure remaining. For really soft, squishy potatoes, cook for 5 minutes.
You can cook more or less potatoes using the same cook time and amount of water.