Sometimes knowing the cause is needed so that you can eliminate it. But we would need more information such as any other symptoms that your husband has, etc. to figure that out. There is a good web site where you list a symptom, like body odor, and it tells you all the different causes and then you rule out which symptoms he dosn't have until you figure out the actual cause. I've had good results sometimes with this website. I left you the link below (wrongdiagnosis.com)
Additionally, people with diabetes sometimes develop a sweet odor. If you husband has not been checked for diabetes lately, I would encourage that he be..
Often body odor is due to dietary causes. He may need to review his diet and eliminate certain things one at a time to see if it makes a difference. If one item removed, dosn't make a difference, then that one will be ruled out and he can try the next one.
Some of the products that are made from algae remove odor from the body. You can find these in health food stores and they go under different names like green algae.
Besides these, the solutions that I found are ones that you may have already tried. I will list them for you though: Hygeine (daily shower with scrubbing and good soap, perhaps something like Irish Spring soap); wearing clothes only once before washing again; changing socks daily and wearing cotton socks.
I hope this is helpful. If you need clarification on anything let me know. I think these websites that I am leaving you can also provide an answer if you look through the different things that can cause body odor. The other website I left you has more home remedies to try. Don't forget that he will need examination for diabetes if he has not had this recently.
Thanks and Good Luck, Susan