Having been a fast food worker, I do know that it is part of the training. The worker thinks it sucks too, but not only is the manager watching, but there are also professional and anonymous shoppers that grade you on a number of things including the suggestive sell.

And it does work. Very well. My personal favorite was "Would you like cheese on those Krystals?" because it was less intrusive, and folks often found that they had meant to say cheese krystals anway.

I often think that everyone should have to work fast food or some other menial labor in one's life because it gives you a lot of insight. If nothing else it is definite inspiration to finish that college degree!