Milk cartons are square and cans are round for the following reasons:
1, milk is easy to deteriorate, so milk should be packed with a composite material called tetra pak paper, which is easy to deform when it is made into a circle, and it is also easy to deform when it is often made into a square.
2. Many drinks are carbonated drinks, which are prone to gas expansion during transportation, and the round shape is more compressive than the square shape.