Right now I'm just putting porcelain ramekins of water in the hutches beside the water bottles. It's the kind I normally use for crème brulee, something like these: https://www.amazon.com/Bellemain-oz...=1513628444&sr=8-3&keywords=ramekin+porcelain
They are heavy enough they won't tip them over and don't freeze as fast. It has only been below freezing a couple of nights and the winters don't get too cold here. When it's cold I put those out in the mornings before work and refill them in the evenings if needed. Otherwise the bottles are fine during the warmer hours in the day, and/or once the temps are above freezing and I remove them and just leave the bottles.
I've got clear shower curtains over the fronts of the hutches that keep direct wind off them, and that helps to keep the water/bottles from freezing as well but still gives them plenty of ventilation on the sides. I've got 3 cages going right now, (7 bachelors, 4 females only, breeder cage of 1 male and 3 females) but if I somehow had them all in one place I'd probably invest in a heated bottle or two so I didn't have to do as much work.
They are heavy enough they won't tip them over and don't freeze as fast. It has only been below freezing a couple of nights and the winters don't get too cold here. When it's cold I put those out in the mornings before work and refill them in the evenings if needed. Otherwise the bottles are fine during the warmer hours in the day, and/or once the temps are above freezing and I remove them and just leave the bottles.
I've got clear shower curtains over the fronts of the hutches that keep direct wind off them, and that helps to keep the water/bottles from freezing as well but still gives them plenty of ventilation on the sides. I've got 3 cages going right now, (7 bachelors, 4 females only, breeder cage of 1 male and 3 females) but if I somehow had them all in one place I'd probably invest in a heated bottle or two so I didn't have to do as much work.