You could suggest (if you're that close) he try some of the standard remedies for serial snorers/sleep apnea sufferers - lose weight, firm mattress and lay off the alcohol. That might improve his night sleeping thus having a knock-on effect.
Of course, it could just be over heating and poor air circulation in the office causing it. Some people seem to be more susceptible to bad air conditioning than others. Modern offices with enclosed air systems and windows that don't open are a big cause.