If work was supposed to be fun, it wouldn't be called work.
I'm sorry to tell you this, but welcome to the rest of your life.
You might find a work that you enjoy MOST of the time, but you very likely won't find one that you enjoy ALL the time.
What I suggest you do is think about the outcome of misbehaving during work (and in front of clients). You might very well lose your job and, as you already know, damage your company's reputation.
Also focus on the fact that after this boring job, another one that is more fun might come your way. And the more focused you are, the faster the annoying one will end.
And, if this doesn't work, try to find another job. But keep in mind that this situation will most likely happen again.