It cannot be put in the freezer. If you put it in even once, it gets destroyed. At least that's what it says in the instructions when you first get it, something I didn't know before I bought it, since it doesn't say it anywhere.

Cleaning it is difficult, but the main problem is that the lid has a wheel for insulation from leaks, etc., which gets filled with dirt from the liquids you put in, and that's why you have to take it out every time to clean the lid (which is difficult to clean because nothing can fit in there), and believe me, the wheel doesn't come out easily... it requires a method and it's not something that can be done quickly. At least it should come out easily.

You can remove this wheel, and the lid still closes quite well without it, but there is a small leak.

Cleaning it is essentially difficult, that's the problem. Better than all the bottles/flasks I've seen on Skroutz, but it's a hassle to clean it every day. I prefer glass jars, but those can break, and that happened to me, so I tried this one, which also has quite good insulation, I would say. Many times it can feel warm on the outside when you touch it, and you think it will be warm inside... but it's cold when you drink from it. It doesn't "sweat" externally.