A cautionary tale:
Don't try this at home but I rode 100 miles on one 500ml bottle and two mugs of (instant) coffee yesterday. Plus a pint of water before leaving.
This ride
I'm generally bad at forgetting to drink/fill up and ran out at about 60-70 miles (coffee was at 50 - with cake at
this lovely place). I made it back feeling OK, and downed a couple of pints of water on getting home at about 5pm. I was craving salt too so I put some salt on my scientific recovery meal (pork pie). I had more coffee and probably some squash in the evening (I don't drink alcohol so just squash).
ANYWAY ... at 3am-ish I woke up with bad cramps in my legs and a thirst. I had several pints of squash and some orange juice during the night and tellingly never needed a wee. I was awake for about 30 min to an hour with this. I'm convinced this was some kind of fluid imblance thing.
All fine in the morning, but I really must remember to drink more often and fill up when possible.