Season flank steak with Adobo seasoning. Set Instant Pot cooker to SAUTE setting over MEDIUM heat; heat olive oil. Cook steak pieces for 2 to 3 minutes per side or until browned; transfer to plate. Add onion, green pepper, Sofrito and garlic; cook for 2 to 3 minutes or until slightly softened. Stir in 2 cups water, tomato sauce, Sazón, beef bouillon and pepper.
Return beef to Instant Pot; add olives and capers. Cover with lid; lock and seal in position. Set cooker to PRESSURE on HIGH for 25 minutes. Turn off heat and manually release pressure according to manufacturer’s instructions. Carefully remove lid. Transfer beef to bowl. Set Instant Pot cooker to SAUTE setting over HIGH heat. Cook for 5 minutes or until sauce is thickened to consistency of barbecue sauce. Meanwhile, shred beef with 2 forks; toss with enough sauce to coat meat. Stir in cilantro. Let cool completely.
Whisk egg with 1 tbsp. water. Lightly brush edges of discos with some of the egg wash. Add 1/4 cup beef filling to center of each disco. Fold over and pinch edges together to seal.
Preheat oven to 400°F. Transfer empanadas to parchment paper–lined baking sheet; brush tops with remaining egg wash. Bake for 15 to 20 minutes or until golden brown and crispy.
Serve empanadas with chimichurri, guacamole or sour cream if desired. Serve leftovers as tacos, quesadillas or burritos.