I use it for cold water. It keeps it cold for a long time, especially if you add a couple of ice cubes, it will definitely stay cold for much longer. The downside is that it has a "metallic" taste, more noticeable when it is at room temperature. It is less noticeable when it is colder. That's why I gave it a low rating considering its price. Compared to other thermoses, it is indeed good at keeping things cool, but the major drawback is that it leaves a metallic taste in the water. I hope it doesn't kill us...

Update: I must say that after a month of use, the metallic sensation in the water is no longer there! (Or did I get used to it?) I highly recommend it for use with cold drinks! And if you add a couple of ice cubes... it forgets to warm up!