Pulse pears, ginger, garlic, soy sauce, brown sugar, and sesame oil in a blender or food processor until smooth. Set half of sauce aside.
Cut sirloin into large chunks. Place in an InstantPot with half of the sauce. Cook on high pressure (manual) for 45 minutes. Release steam and shred with two forks. Serve with remaining sauce as tacos, over rice, as sandwiches, or as a salad.