Place the olive oil, lime juice, sugar, salt, cumin, garlic, water, smoked paprika, onion powder and chili powder in a gallon sized resealable bag or large bowl.
Whisk until thoroughly combined.
Add the steak to the marinade. Marinate in the refrigerator at at least one hour, or up to 6 hours.
Preheat an outdoor grill, grill pan, or skillet to medium high heat.
Add the steak and cook for 5-6 minutes per side for medium doneness. Remove from grill and let sit for 5 minutes.
While the steak is cooking, make the avocado topping. Stir together the avocado, red onion, cilantro, lime juice and salt in a small bowl.
Thinly slice the steak against the grain. Divide the meat between the tortillas. Top with avocado mixture and serve.