Combine 1/4 c. jalepeno juice, 1/4 c. avocado oil, 2 Tbsp. cilantro, 2 tsp. garlic, and 1 lb tilapia in a gallon sized zip top bag. Marinate at least one hour, or for as long as overnight.
Combine shredded cabbage, sour cream, lime juice, salt, pepper, 1 Tbsp. chopped jalepenos, and green onions in a small bowl. Stir until well combined. Set aside.
In a large skillet, heat remaining avocado oil. Add marinated fish. Cook 4-6 minutes, stirring frequently, or until fish is opaque and cooked through. Add fish, cabbage slaw, and any remaining cilantro to corn tortillas.