I use plastic Igloo water dispensers, the kind that look like a cylinder, with a pour spout on top and a handle on top. Fairly easy to manipulate and pour carefully. The spout gives me enough control that I can even water a houseplant or fill an ice cube tray. I have two of those. They come in a nylon cloth sleeve.
I always have an empty 2-liter bottle by my bedside, as I tend to wake up thirsty at some point during the night now. They are easy to keep water-tight and uncomplicated to open and close when I'm bleary and mostly asleep, plus easy to tuck into smallish spaces. And I keep an extra one full of water in case I space out and forget to fill the first. If I want a quick drink or have no time, it's easiest to handle smaller containers.
I've looked at the 5 gallon and 7 gallon water containers at our local stores and online, but they look huge and hard to either store or use. Some of them are extra bulky because they have giant handles too ... I just find it easier to have smaller, easier to store containers. And if I ever need more or less I just buy or throw away a 2-liter bottle.