Fizz! Dancing sultanas! Try this at home! Density and a reaction.

Density is a scientific property that can tell you if something will sink or float.

Sultanas are more dense than water so they sink when put into the glass of water. 
Vinegar = acid
Baking soda = alkaline

Vinegar and baking soda react together to form a gas called carbon dioxide which is released in the water in small bubbles.
Some bubbles rise to the top of the glass because they are less dense than water.

Some bubbles become attached to the wrinkles on the sultanas.

If there are enough bubbles trapped on the sultana then it becomes less dense and increases in volume so the sultana rises to the top.

When the sultana reaches the top of the water the bubbles burst and the sultana is back to being more dense and sinks.