Yep they are. My kids each had their thermos container (the bigger one) in their bag.
It was great since I would, fill it with ice in the am and slowly add the cold (bottled) water and they still had ice cold water when I would go fill them later that night after our break. We went in August.
Dh and I just had the double insulated plastic water bottles and the ice melted much quicker but it wasn't steamy hot.