Sweating at night can be caused by many things.

If you are using a fatburner with ephedrine this can make you sweat big time.

If you drink some tea, or some green tea or any other hot beverages that can also make you sweat big time.

If you are nervous, stressed out, or sick with a virus.

I do beleive that sweating can be related to weightloss, not only water loss and i have some proof.

When you have a fever your body temperture is elevated so your body burns more calories then normal, same thing happens when you use a fatburner.

Same thing happens when you take a sauna or hot bath, but your body temperture is elevated for a short amount of time, not like when you have a fever and you sweat all night.