1. Combine tequila, triple sec, lime juice, garlic, salt, and oil. 2. Place fish in a single layer in a flat dish. Pour tequila mixture over, and marinate for 1/2 hour at room temperature, or 3 hours in the refrigerator. 3. Just before serving, combine tomatoes, onion, chile, cilantro, sugar, and salt to taste to make fresh tomato salsa. 4. Remove fish from marinade (reserve), and pat dry. Brush fish on both sides with oil, and grind pepper over it. 5. Cook on greased grill over high heat until flesh is opaque (about 4 minutes per side). 6. Boil sauce in a saucepan for about two minutes, remove and discard the garlic cloves, and spoon over fish. 7. Serve alongside fresh tomato salsa.