Apparently, you are required to think of a sequence of pouring operations, after which the containers will become filled as required.

The guy said that some people, given a deal of time, did solve it so it shouldn’t be much of a problem for me. As he was explaining the puzzle, I was wondering whether it would take anybody more than few seconds before he/she can figure an answer, but it seems this wasn’t quite the case.

I hurried to attend my circuits’ lecture, which has already started by then, took a seat and immediately started working on the puzzle. To my surprise, I spent about fifteen minutes thinking and couldn’t get an answer. I was starting to question the validity of the containers' sizes when suddenly a cool fact came to my attention …

The build of this puzzle can be exploited to get the answer!

During those 15 minutes I was fooling myself for thinking! At no point I really had to “think” about the next step of solution. Try it yourself, the first step is pretty clear: pour water from the biggest container into one of the others. At every subsequent step you find yourself ahead a number of choices, all of which, except for the correct one, are pointless, and do nothing but probably take you few steps back. You don’t need to think because the right step is always so obvious; the other “choices” never make sense, and are only there to mislead you.