Dancing Raisins

We put some raisins into bottles of Sprite Zero, and Soda water.
We noticed:
The raisins had little bubbles on them.
Lots and lots and lots of bubbles were coming off the bottom.
The bubbles come up but never go down.
When you opened the bottle, there were a few bubbles, but when you added the raisins, it started exploding!
The raisins went up and down in the Sprite.
When the Sprite exploded the raisins kept going down.
The top of the Sprite was like a shield and the raisins coudn't get on top of it.
Near the beginning, when the bubbles went up they stayed on the top for ages. Then the top went all white.
The raisins that went to the top were covered with bubbles.
When you opened the brand new soda bottle, it exploded like a volcano.
As soon as you put the raisins in the Sprite bottle it overflowed.
The raisins in the bottle were getting wrinklier. They looked weird.
The Sprite bottle had more bubbles than the soda bottle.

We thought:
 The carbon dioxide or air was escaping. Less bubbles came up as we did it.
We think the bubbles made the raisins go up and down.