The best diet for a pet rabbit consists of high-quality hay, such as timothy hay, fresh vegetables (e.g., leafy greens like kale and romaine lettuce), a small amount of pellets formulated for rabbits, and fresh water. It's important to provide a variety of foods to ensure they receive essential nutrients. Avoid feeding rabbits foods high in sugar or carbohydrates, as well as human foods that are toxic to rabbits, such as chocolate and avocado.