Cook beef until no longer pink, 5 minutes. Drain. Mash beans.
Sauté onion 5 minutes. Add jalapeños, garlic, cumin, chili powder. Cook 30 seconds.
Stir in beans, tomato sauce, water, cilantro, salt, pepper, and beef. Cook until thick, 10 minutes. Cool 20 minutes.
Soften tortillas. Fill with 3 tbsp filling. Roll tightly.
Fry taquitos at 350°F until golden, 5 minutes per side. Keep warm in oven.
Mash avocado, sour cream, water, lime juice, and cilantro. Season.
Serve taquitos hot with avocado sauce.