Originally posted by Chris L
To put it simply, that was never going to be enough. If you haven't eaten properly, I'd advise simply not riding until you have. Another thing you probably didn't do is drink enough water through the day. During summer around here, it's not unusual for me to go through 10 litres of water in a day. Drinking before the ride means you've got more in reserve when you start.
I would never leave the bathroom! I'm doing good to get 1.5 litres, of course, I'm probably only doing 1/10th of the workout you do. I can tell a difference when I haven't had enough water. The last few days I have been drinking less because I haven't felt that thirsty and my head is paying for it this morning.