My typical ride is about 40 miles which takes me about 2 hours. I take a bottle of Gatorade with me and most of the time I bring it home 3/4 full. And that's on a hot day. A 3 to 5 hour ride I take energy bars and drink lots. I try to to pace drinking and eating so that I have the energy to finish. On my 130 mile ride I had to use a couple of gels to get over the hills on the way home.
In reference to an earlier post, if you are interested in losing weight 3 to 4 hour rides really burn the calories especially if you eat in moderation during the ride and after. I once went from 235 lbs to 165 in one summer doing just that. I find a century ride really makes me loose weight no matter how much I eat during the ride.
In summary, on a 2 hour ride just a little water or Gatorade.