You can use coins to rent certain clubs from the pro shop.
You can use them to play in the H2h coinrooms, for example to help your club win turf wars.
You can use them to upgrade your apparel , when you have played your sponsorship , you use coins to progress the apparel in each sponsored clothing . The points you win for apparel won’t on their own buy you the enhancements , you need coins to do that .
Other than that not much use.