Steak Fajitas with Fresh Guacamole

Name: Steak Fajitas with Fresh Guacamole
Ingredients: 1/4 cup soy sauce; 1/4 cup red wine vinegar; 2 tablespoons light corn syrup; 1/2 teaspoon hot sauce or more to taste; 1/4 teaspoon ground black pepper, plus more for seasoning; 12 ounces leftover flank steak slices; 1 green bell pepper, seeded and cut into thin strips; 1 red bell pepper, seeded and cut into thin strips; 1 onion, halved and thinly sliced; 8 tortillas; 2 ripe Hass avocados, peeled and pitted; 1/2 cup diced canned tomato; 2 cloves garlic, minced; 1 large or 2 small limes, juiced; 2 tablespoons torn or chopped fresh cilantro leaves; Salt