Place the chicken in the Instant Pot. Season with garlic powder, onion powder, salt, and pepper.
Add 3/4 cup of chicken broth and 1/2 cup of Caesar dressing to the pot.
Place the lid on the Instant Pot and lock it. Make sure the lever is set to seal. Press the manual button and set the time for 10 minutes.
When the time is up let the pressure manually release for 10 minutes, then release the pressure and remove the lid.
Use two forks to shred the chicken. Add 1/4 of the chicken mixture to each hamburger bun.