Best thing I've always carried is a bandana. Got to use it as a tourniquet on someone who had crashed, at full speed going into a curve, into and over a guard rail.
Great on a hot day . . . soak it in water and use as neck/forehead cover. Use it as a rag if need be. Water in waterbottle can be used to clean up cuts/roadrash. Also carry couple ibuprofen/aspirin.
Make up your own mini-kit and always carry it.
Better to have it and not need it, than to need it and not have it.