Maybe you were dreaming about going for a big long ride
Drinking too much plain water can also lead to cramps as it depletes your body of salt. A sports drink can really help. I like Endura (lemon-lime, powder form - works out to be under $1 per 750ml drink bottle refill, much cheaper than buying bottles of powerade or gatorade). It's great in the hot weather when I'm exercising and know in advance that I'll be sweating a lot. It's not sickly sweet either, if anything, slightly salty.
Enjoy your bike riding... I just dusted mine off recently and have ridden to work a few days (not this past week though -- too hot). It's only about an 8km, but I really struggle on the way home as it's mostly uphill. People pass me all the time
It's also a bit scary being in so much city traffic
... and I mostly ride on bike paths.
What are you bike riding plans?
Just keep moving! And don't be lazy...
SW: 74.3kg - 1/1/09
CW: 71.1kg - 3/5/09