In the Instant Pot, combine the water, tea bags, boba pearls, and sugar.
Secure the lid on the pot. Close the pressure-release valve. Select MANUAL/PRESSURE COOKER and set the pot at HIGH pressure for 5 minutes. At the end of the cooking time, allow the pot to sit undisturbed for 10 minutes, then quick-release any remaining pressure. (If the pot starts to spew liquid, close the valve and try again in a minute or two.)
Remove the tea bags and stir in the evaporated milk.
Fill four glasses with ice. Pour the tea over the ice, evenly distributing the boba pearls among the glasses. Serve.