A new Cadbury's chocolate drink?
It's certainly unusual for Sainsburys to have a new product on the shelf days before its official launch. They usually take months to get new stuff. They must have been given a big back-hander to stock it.
They also had the new Cadbury's share boxes straight away. Like Oldspice, I've noticed Sainsbury's normally don't take on new products for ages, so I think there is definitely a deal going on here.