I seem to consume a lot of water and burn a lot of calories. 1 litre about every 20 miles and around 800-1000 calories per hour, however, I am generally at between 85-95% of my HRmax.
When on the MTB I can do without food or drink due to the intermittent effort, on my road bike when training I always pushing.
I've started using carb powder in my drinks and electrolyte to stop the headaches and a good glass of milk when I get back.
Fig rolls are great but I too eat the packet/s.