You can require participants to add a sticker of a major sponsor to thier boat. They are almost always on supplied boats at big events. In a BYOB event the organizers can word the NOR so the sailors must put on the sticker to race. Most normal people won't complain when they find out a major sponsor has given the event a substantial amount of money to help run the event. Having the sponsor buy sails or things like that doesn't do the event any good when you have to pay the bills.
