This is an old sweet which I haven't seen in a long time. It used to come in dark pink packets and with 'pop out' words in batman style 'pow' lettering it said FIZZ WIZZ!. The packets were the size of the little sticker collection add-on pack sets. The top would be ripped off, revealing the shiny silver inside and the little pink blobs ready to be poured into your mouth.
The mouth would be opened, and with one swift movement. The contents would be poured inward and the head tilted back.
The little blobs would all then start to pop and explode. Then you would start rummaging through the little pack, scouring it with your eyes looking for blobs which escaped your giant hole. Especially looking for the bigs ones, as they made the loudest noise.
Whenever I had a pack of these (about 5 years ago was my last one). I always used to walk up to people, open my mouth next to their ears and say 'can you hear it'. To which they would reply 'no'. 'How about now?' (opening mouth wider) A large one would usually go off at that point. And being the young child that I was, would squeek with delight and go 'WOW that was a big one!'...

oh the joy, I want a fizz wizz now. The closest thing available now (I think) is willy wonka's exploding chocolate. Which is rather disgusting, the combination of chocolate with Fizz Wizz is one not to be desired.