AFAS allowes you to pay cashless inside the whole venue, you can pay with your debitcard or creditcard. Would you rather like to pay cash? Get a special prepaid card and use this to pay! You can get this card with cash your debitcard or creditcard at the cash registers. For more info, check this page.
Do you still have an amount of money on the prepaid card at the end of the event? Check this page on how to get a refund.