I think the point is that you're trying to hold back something your brain has already processed as funny, and the more you try to control yourself the more impossible it becomes. It's like when someone tells you "don't laugh" and suddenly everything becomes hilarious. The hardest part is that you know the brand name correctly, so the gap is even more obvious when you hear the mangled version.
Honestly? I don't know if there's really a way not to laugh. Maybe the real trick is just not to force it - accept that it's a natural human reaction and that laughing about it isn't mean-spirited. Then, once the laugh comes out, usually the awkwardness passes and the whole thing becomes less of a big deal. Your coworker probably doesn't even notice that you laughed at them.