Prince Lionheart (Babies R Us) makes a kit that has two clips, a snack holder, drink holder, hooks and mesh bag. The problem is that the clips have to be places just right in order to close the stroller, and often you have to remove the holders too.
There are leash type things that can hold a bottle of water/sippy cup which can be hooked on to a stroller. I got a Maclaren organizer which is a mesh pouch with two neoprene drink holders and hangs from the handles of my umbrella stroller. You really have to wiggle a bottle or cup in it, and it sort of flops backwards a bit, but still works. Just keep in mind too that any added weight on a back of a stroller could make it tipsy, especially if a child isnt in the stroller.
Im going to try something with my stroller. I bought a doggie treat pouch with clips and am going to rig it so that my daughter can reach in and get some snacks. As for her sippy cup, I have a leash type thing from the Right Start that loops around the stroller and her cup. She will have to have the cup tucked next to her, but at least when she tosses it out it wont get lost!
alison