Well, I mainly use water bottles, but on longer rides out in the middle of nowhere I take along a hydration pack, especially on hot days. It's not unusual for me to go through both bottles and most of the 2 liter hydration pack on long rides during the summer.
And I don't stop to take a drink unless I'm taking a break or something. Not because I'm in a hurry to get anywhere, but it just seems like a pain in the butt to stop every time I want some water. So I either reach down and grab a bottle or I unclip the hydration pack straw and drink from it.