When you spin the reels, cherry bubbles may randomly appear and will float around the screen.
They are harmless soap bubbles and you can safely ignore them. However, when you pop them, they sometimes reveal free coins!
Sometimes the bubbles reveal a bigger reward, and then the app will offer you to watch a video ad to increase that reward.
There's no special meaning to the fact that there are cherries inside the bubbles.
The content of the bubbles is not bet dependent, and the frequency of bubbles is random. Sometimes there are many bubbles all at the same time, and sometimes there's a long time between bubbles.
Bubbles only appear at a minimum bet of 300 or 500 coins.