Glass bottles are used for lots of recipes in Cryofall. The recipe isn’t super obvious, but it’s simple once you figure it out.
First, go gather some sand. Next, you will need ash from previous cooking or smelting in the furnace.
Take sand and ash and cook it in the furnace to craft glass fragments.
Take the glass over to the Workbench. Craft a glass bottle for 10 glass fragments.
Now you are free to either take water on the road, collect saltwater, and craft many other recipes. (crafting ammo for example will require paper, which needs wood and a glass bottle filled with water) Easy peasy!