Heat a large skillet over medium-high heat. Cook and stir beef in the hot skillet until browned and crumbly, 5 to 10 minutes. Drain and discard grease. Mix taco seasoning into the beef.

Crush chips without opening the bags. Open bags and spoon in seasoned beef. Cover with cheese, tomatoes, lettuce, and sour cream. Stir to blend. Eat with forks right out of the bags.