Often I'll drive straight from work to the lake for a club bikeride or to ride solo.
I pack the car with bike, clothes, shoes, all my bike stuff.
I take 2 waterbottles into my workplace to fill with ice/water on my way out.

I do keep a spare bottle at work, but one 24-oz bottle isn't enough for a hot summer ride.
On our club route, there isn't a place to refill bottles mid-ride with cold water.
Dehydration is a chronic issue with me.
Borrowing a bottle from a friend isn't an option either. They need both their bottles too.

No water = no ride. And insufficient water = no ride.