Soda contains molecules that are forced into a mixture with water molecules because of the pressure. Opening the can of soda will release the pressure, which allows the to escape from the mixture and form bubbles.

The soda bottle contains water and carbon dioxide as gas.

When we open a soda bottle we observe a fizz, this is opening of can of soda and releasing pressure. the carbon dioxide gas escaped out from the can.

This escaped carbon dioxide gas is the fizz or the bubbles observed during opening of soda can.