Preheat oven to 325 degrees. In a large skillet, brown meat and drain off fat. Stir in beans, tomatoes, onion, taco seasoning, soup and water. Simmer over medium-low heat until everything is well combined and heated through.
Grease a 9×13 casserole dish. Put down a layer of crushed tortilla chips, followed by a layer of the meat/bean mixture, then half of the cheddar cheese. Repeat layers. Cover with foil and bake for 20-30 minutes, or until bubbly.
Let sit for 5-10 minutes before serving. Top with sour cream and salsa.