The cookie jar is just a clear glass canister. I got one like that because it's similar to his little 2 gallon aquarium (only a lot smaller). He tolerates the cookie jar because it gives him enough room to swim around in. Plus I put a small plant and a little gravel in it. He hates being in the small cup that I put him in when I change his water, though. Probably because there is barely enough room in there for him to move around, plus I don't put anything else in it with him. But he's only in that for a few minutes and then I put him back in the tank when it's clean.
Totally sweet.
It's one of the nicest things I have ever heard anyone do for a fish.