If all you want to do is carry water and a tube, it really doesn't matter what small pack you get. I've found the Camelbak branded bladders to have good flow and a simple bite valve, so I'd suggest one of those.

If you want to size up and carry more stuff, then brand and design gets a little more important as it's more about how your pack carries weight, and how that weight moves around during biking. In which case, the premium options are the Wingnuts and Ergons- lots of quality design, but pricier and a bit harder to find.

Again, if you just want to carry water, get something small and cheap. I've had 5L MEC and Decathlon (buget Euro brand) bags that have lasted years and functioned well.