I don’t have any qualifications. But I have fasted since age 7 and have many years of experience.
I still do t understand why do you think you will have fever?
This is also a very common practice, when one has fever, they try to keep them warm to make them sweat and bring the body temperature down. You can sleep naked, it does help lymph flow better, but then it also flows better with loose clothing.
To move your lymph better, you may do dry brushing on your body, take hot and cold showers, deep breathing, and moderate exercise.
If you are fasting then your sleep will be erratic.