In a resealable plastic bag, combine the cola, olive oil, 2 tablespoons lime juice, the chili powder and 1 1/2 teaspoons salt. Add the steak and let marinate at room temperature for about 30 minutes.
In a large bowl, toss together the tomatoes, onion, cilantro, jalapenos and remaining lime juice; season with salt.
Preheat a grill or grill pan to high. Grill the steak, turning once, about 15 minutes for medium-rare; let rest for 5 minutes. Thinly slice the steak against the grain and toss with the tomato salsa. Fill each taco shell with some slaw mix, an avocado slice and steak with salsa. Serve with the lime wedges.