Place the beef bones and brisket into the Instant Pot. Add the halved onion, ginger slices, star anise, cloves, cinnamon stick, salt, sugar, and water.
Close the Instant Pot lid and set the valve to the sealing position. Select the 'Pressure Cook' setting, adjust the time to 45 minutes, and start the cooking process.
While the broth is cooking, prepare the rice noodles according to package instructions, usually soaking them in hot water for about 15 minutes until tender.
Once the cooking time is complete, carefully release the pressure using the quick release method. Open the lid and remove the beef brisket; set it aside to rest.
Strain the broth using a strainer or cheesecloth into a large bowl to remove the solids. Discard the solids and return the clear broth to the Instant Pot.
Shred or slice the rested beef brisket and add it back to the broth. Taste the broth and adjust seasoning with salt or sugar if necessary.
To serve, place a portion of the cooked rice noodles into a bowl. Ladle the hot broth with beef on top. Garnish with fresh herbs, lime wedges, and jalapenos, if desired.