Replace the tires if they are cut or badly worn. Cable and lock for bicycle. Personal medications, ibuprofen, etc. Food and drink generally require cash. Most of the major vendors of bike repairs, accessories, souvenirs, clothing, etc., accept VISA and MasterCard.
Ambulance services are available throughout the ride for serious injuries.
Some bike shops maintain mobile repair units along the route each day as indicated on your route maps. Bike repair may require a wait. Pricing is probably about equivalent to typical urban bike shops. Sag service is provided by the Register. Neither Cornell nor the individual organizers accept any liability for your personal health and safety.