During my last trip, I didn't have enough time to rent a bike, and honestly, the road that goes through the sandbar doesn't seem too suitable for bicycle wheels, so I can't fully recommend it. Just wanted to inform you that there is such an option (perhaps you might want to use it in other parts of Amanohashidate, not just the sandbar). The price for renting a bike for 2 hours is 400 JPY.