The best way to exercise a pet rabbit is to provide them with a large and safe space to move around freely. This can include a rabbit-proofed room or a secure outdoor enclosure. Additionally, you can encourage exercise by providing toys for them to play with, such as tunnels, balls, or cardboard boxes. It's also important to allow your rabbit time to hop and run around outside of their enclosure under supervision. By providing a stimulating environment and opportunities for physical activity, you can help keep your pet rabbit healthy and happy.