The cereal box pictured a nearly naked woman on a pole. She only wore the barest of thongs.
The back of the box announced the prizes inside were trading cards of people having sex. One trading card picture was included as an example: one fat old guy fucking another fat old guy doggy style.
I just googled TriXXX cereal but I don’t see any examples immediately available. Someone somewhere must have some example of a cereal box like that. The internet being the internet.