Ok that’s up to you how you wanted I have two custom fields Mobile , Customer Id , create barcode add to customer id so when the card with barcode scanned account selects, or search with phone , name , mobile anything you search you will get account to ticket.
Do you mean you don’t want extra entity type and use customer for loyalty? you need to lookup main thing account type (debit/credit) . Do you want provide them food and they will pay later? or use the funds what they had in account ?
You will find what you need in forum spend some time to read those
look at this post