i'm not a lawyer either, but i don't think a player can sue the casino for misleading marketing unless he is directly affected, like if they advertise a game being 1% house edge, but it's not, etc... and unlike the red bull case, where a customer bought the product with their own money, the case here is just a "fake" freebie.
but regulators on the other hand, could slap them with a fine, which they would obv keep for themselves. again, i'm not a lawyer, so i could be wrong with my assumptions.
You're right. Some case I could think of was when a radio station offered a $250,000 prize for a forehead tattoo of their logo (which was supposed to be an April Fool's prank), but, well, someone actually thought it was a legitimate offer. One guy got a tattoo on his forehead, a big bold KRUD (radio station's logo). He then went to the radio station to claim the prize, but the staff told him it was just a prank. He was told that on their website where the announcement was made there was a tiny link that if clicked, would've told him it's part of an April Fools' prank.
He took them to court, and earned $510,000.

Here's a short video clip of it:
https://www.youtube.com/shorts/htarawfgKeg