Unity removing meshes/triangles on specific area of ridigbody

How can I achieve this kind of action? I need to remove meshes when I swipe or click some object. How can I remove meshes of cube or any blender object.

https://i.stack.imgur.com/sKiPe.png

like the game : sand balls

https://play.google.com/store/apps/details?id=com.water.balls&hl=en_US