In a medium bowl, whisk 2 tbsp. fish sauce, the soy sauce, 2 tsp. sugar and the pepper; toss with the beef. Let marinate at room temperature 30 minutes.
Preheat the oven to 250°. On a rimmed baking sheet, arrange the beef in a single layer. Bake until dry but still pliable, 1 hour 45 minutes to 2 hours.
In a small bowl, stir the chiles, lime juice, garlic, the remaining 2 tbsp. plus 2 tsp. fish sauce, the remaining 1 tbsp. plus 1 1/2 tsp. sugar and 2 tbsp. plus 2 tsp. water. In a large skillet, heat the oil over medium. Working in batches, fry the jerky until heated through, about 20 seconds per side. Serve with the garlic-chile fish sauce and sticky rice.
Note: If you want a more classic beef jerky, just cook through step 2.