Its all in the eating and drinking
I did one (85 miles) 2 weeks ago and died
then one week ago same route but ate a small risoto (left overs) at 5.30 am b4 I got on the bike
a banana 30km , a bacon and egg s/wich and muesli bar at 80km , and a banana at the 100km
plus 3 bottles of gatorade , 2 water
and it was a cool day with little sun
So in essence, if your thirsty your allready de hydrated, you should be drinking a bottle an hr
and find food for fuels that will sustain you