It is not that easy, we do not know the fact because some streamers may not tell you the fact about the money. Even if the streamers tell me the source of their gambling funds, I would not trust it easily.
Overall, I do not really care where the money comes from because I take those streamers as entertainer only. It is fun to watch people win big on gambling regardless they use sponsored money or their own money.
Yeah, it's not simple to tell who's using their own money or the money of sponsors, and it doesn't matter because what counts to us is how beneficial the platform where they play is, and, of course, their reputation.
Entertainers/streamers will do everything on their power to get more money, will lie if they can since it's their job.
In case you couldn't take the streamer's words then just assume the funds are sponsored, treat what the streamer did as merely entertainment, and do your gambling habit as usual. I think people are not that so fool until would follow everything that streamers did.