Kleen Kanteen sells non-insulated metal bottles as well; I've used them for this purpose (not sleeping, but holding against my body to help stay warm in a cool

Kleen Kanteen sells non-insulated metal bottles as well; I've used them for this purpose (not sleeping, but holding against my body to help stay warm in a cool room). Bonus: once the temperature drops far enough you can also drink it for a quick internal thermal boost, if needed.