I am not a physician, but a mom of a child with diabetes. I do know that the heat can and does affect your blood sugars. I know that people with diabetes need to be careful in hot tubs and saunas. I will do some research for you and get back to you with more information.
I did a little research on your question because you got me to thinking. I have had type 1diabetes for 7 years and thought this sounded familiar.
There are some forms of neuropathy that can cause excess perspiration. Because some neuropathy's can affect the nerves that control organ and glandular systems and sweat comes from a glad so that would make sense. If you don't know what neuropathy it is is when nerve damage occurs due to poor control of blood sugars for an extended period of time.
It might be worth talking to your doctor about. The particular form of neuropathy that causes this kind of complication is called "autonomic neuropathy."
Hope this helps
ndninformer- I agree with pump girl, contact your doctor, as I was not able to find anything different than pumpgirl03.