Well, we're not fancy, we usually just throw a few of the kids' plastic contigo bottles in our backpack with some low, flat bottom, rectangular "tupperware" containers from Ikea. We get the $5 multi-size pack every year for the kids lunches- the little sizes are awesome for that purpose, the large sizes are awesome for storage, but, this is the ONLY thing that the middle, low, not quite big enough for leftovers or cookies or muffins size is good for, though! FWIW, they've never managed to knock them over, and they LOVE to knock over their un-tippable SS water bowl at home.