I mix about 1/4 cup ACV with 1 3/4 cup warm water. I know some people do it stronger than others. I find this ratio works for me but you can play around, to see what makes your hair feel its best. If you search "ACV rinse" you should find a bunch of threads on how people do theirs. Oh, and if you have shorter air, you don't need 2 cups of rinse. I have dense hair that is bra strap length and I find 2 cups is more than enough.
HTH and good luck!