Line the Instant Pot with aluminum foil to make removal of the ham easier.
Sprinkle half of the brown sugar on the bottom of the foil in the Instant Pot. Place the ham on top of the brown sugar.
Arrange the pineapple slices over the ham. Pour the pineapple juice into the instant pot for the cooking liquid. If there isn't a full cup of liquid, add water to make up the difference. Sprinkle the remaining brown sugar on top of the ham.
Secure the lid and set the venting valve to seal. Set the Instant Pot to HIGH for 15 minutes. It will take about 20 minutes for the Instant Pot to pressurize before it starts counting down the time.
Once the timer goes over, do a quick release by turning the sealing knob to vent the pressure. Remove the ham and pineapple slices from the Instant Pot and serve immediately.