I'm thinking about telling my workmate that he stinks.
Why would you be so brutal?
He is nasty and he always burps
I think that there is a nicer way to go about this. Being that harsh is going to hurt his feelings.
I already did it, and it was fun.  It's not my problem if he gets hurt feelings.
I really hoped that you would care about the feelings of others, even those who are disagreeable.  However, I still have to advise against this kind of behavior at the workplace.  If you get a reputation as someone who is rude and insulting, others will not want to work with you, and this will hurt your chances for advancement.