The seat tube on small frames may be too short to hold a water bottle. This is exacerbated by modern, sloping top tube designs that result in a short seat tube.

If not, you can use clamps to attach a bottle cage to the seat tube or handlebars, and other mounts are available to hold bottles behind the saddle. Or a "camelback" bladder you can wear like a backpack.

In short, there are options for you to easily carry more water.