Not sure but maybe it's a particular food? Maybe you could find out by starting on a monodiet and using a method like the elimination diet... something where you add a food back in at a time nad see if the night sweats commence? Also, there is some eastern ideology about cold and hot associated with foods. I don't really understand it but I've heard snippets: bluberries/bananas - cold (not physcially cold but things that affect you in the balance of cold/hot). Maybe delving into that might get you some answers.