I swear by my collapsable silicone water bottle. It hangs from my belt loop and can be rolled up toward the end of the day when I don't need anymore hydration. It easily forms to the extra spaces on ride seats with little to know fuss, so I don't have to remove it when seated. I have a 17 ounce version, because I don't want to lug around a great deal of extra weight at any given time. There are fountains and vendors to replenish everywhere, so why bother. You can get them in larger and smaller sizes though. It is a bit of a challenge to get the last few drops of water out of the bottle, some squeezing is required, but as with the size issue it's just a matter of getting filled up again.