Heat a large skillet over medium-high heat. Cook and stir ground beef in the hot skillet until browned and crumbly, 5 to 7 minutes. Drain and discard grease; remove beef to a plate and set aside.
Cook onions, bell pepper, and garlic in the same pan over medium heat until peppers are soft and onions are translucent, making sure not to brown or burn garlic, about 5 minutes. Add beef back into the pan and stir to combine. Add tomatoes, sofrito, and raisins; cook until softened, about 5 minutes.
Stir in chicken stock, tomato sauce, cilantro, olives, sazon, oregano, cumin, salt, and pepper. Bring to a boil. Reduce heat to medium-low and cook until thickened, 15 to 20 minutes. Remove from heat and let mixture cool slightly, 15 to 20 minutes.
Combine beaten egg and water in a small bowl. Spoon filling mixture evenly into the middles of the thawed empanada discs. Brush edges with egg and water mixture, fold in half, and seal the edges with a fork.
Heat oil in a deep-fryer or large saucepan to 350 degrees F (175 degrees C).
Fry empanadas in the hot oil, working in batches if needed, until golden brown, 4 to 6 minutes, turning halfway through.