What Causes Foul Smelling Excessive Sweating?

Good Morning. My husband is 27 years old, without any known chronic illnesses. He is 1.67meters ,average build and has a job that keeps him very active during the day. At night he sweats so much to the point where he soaks the sheets and blankets. What worries me is that it smells like vinegar. He never has any body odour any other time. He practices good hygiene but this sweating comes from all over his body... back, chest, arms, legs. It has been this way only for 3 months. It literally smells like vinegar but he complains that he is getting cold. What could be the cause of this? He drinks alot of water, does not drink alcohol, and smokes cigarrettes.