Remove the corned beef from the packaging, rinse off the salty brine.
Rub brisket with the enclosed seasoning packet.
Use my Corned Beef Seasoning packet recipe to make more in necessary.
Add two cups of water to the Instant Pot.
Place rack in the Instant Pot and add the seasoned brisket, fat-side up.
Top brisket with sliced garlic and onions.
Pour 12 oz bottle of beer over the brisket, sprinkle more corned beef spices if desired and seal.
Cover and set the vent to "seal." Choose "Pressure Cook" option and adjust the time to 90 minutes.
The pressure cooker will take approximately 15 minutes to seal.
Let pressure release naturally for 15 minutes, then manually release the remaining pressure.