Does sweating cause weight loss?

Yes. People do, in fact, lose weight by sweating. However, this loss in overall body weight does not directly lead to long-term body mass reduction, as sweating merely releases liquids within your body’s cells and tissues rather than eliminating fat storage.
Only temporarily! Sweating causes weight loss because sweat is water, and water weighs 8 pounds a gallon. However, if after sweating, a person doesn't drink water to replenish himself, his body will be somewhat dehydrated. If a person sweats a great deal, and doesn't drink much at all, he can get heat stroke and die of hyperthermia, so one should always drink water to replenish oneself.