Agree 100% with KaraCooks, no impact on weight loss other than water.
I will add this note though.
I actually use a sweat suit about once a week/2 weeks at the gym. I sweat buckets when I use it so have to be really careful to hydrate well before, during, and after use.
For some reason it feels really good to me to have a really good sweat every once in a while. I used to do this in a dry sauna every once in a while but don't have that available at my current gym.
It's hard to describe, but sweating out a bunch of water and replenishing it gives me kind of a cleaned out feeling. I'm sure there is no real science to it, but it does feel good to me.
Be aware that it can be dangerous if you overheat, or if you don't stay hydrated. I would not recommend it for any impact on true weight loss.