You can get guitar and string cleaner kit from a music shop.. It would not hurt to wipe down string often during practice if sweating is that profuse.. The stains may be body oil more then moisture. Good rub down on the with lemon oil when you change string would be helpful also. I use a silcon paste, but I have heard that it not good if you ever need refinish work.
The strings also last longer if cleaned.
Happy cleaning and guitar playing
Gordon
