my first winter with chickens, we had a nipple system to a stock tank inside the shed. i put a stock tank heater in it to keep the water from freezing. i think you can do the same with a 5 gal bucket that has nipples
I use heated waterers but here is a cool article on other methods https://www.backyardchickens.com/articles/alternate-method-to-prevent-water-freezing.73180/