What Causes Excessive Sweating Along With Fever When Suffering From Stomach Infection?

My son is 25. He is finishing an antibiotic, minocycline, for a sore throat/sinus for the past week. He developed a bit of the stomach flue with aches etc on top of that. (It went through the household) The last two days he has been having bouts of profuse sweating and some fever and chilling. Last night he soaked the bed with sweat. He is working today but said the sweating is very frustrating and started urinating a yellow/gold this morning. He works long hours but he has been extremely fatigued.