Why do you have to make two holes in a can of condensed milk to drink it?

In order for the air to push the condensed milk out of the can, since the atmospheric pressure is greater than the pressure produced by the milk in the can.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.