I take a small Nalgene (~500mL size) touring, the larger sizes I use hiking+backpacking. The small size works great for me, just rite for carrying while off bike doing touristy stuff. I also made a "cozy" for it out of Reflectex insulation. The "cozy" keeps my coffee, tea, or cocoa piping hot for a long time when I want it to be, and juice/eletrolite drinks/water chilled for a bit. This size fits perfect in my cages (sans cozy), particularly in my third cage-where 1L bottles don't fit (under the downtube).

I've also made a "cozy" for my cook/food bowl. I simply use those Gladware brand disposable bowls with lids. One of the round sizes, with the "cozy" nests inside my cook pot (an Isobutane canister nests in that). I just add boiling water to oatmeal, ramen, instant soups, rice & such. Foods that may need a few minutes of simmer time continue to cook when I close the bowl lid (with an insulated top). Easy&sanitary food prep&clean up.

The "cozies" are simple to make, cut strips of the insulation (found at any Home Depot/hardware type store), tape+all done. I use aluminum foil tape, but good old duct tape would work as well. They hardly weigh anything. I use the remaining Reflectex as intended, for insulation.