Air in the Box
I bought this big box of Kellogg’s Crunchy Nut, but it was too tall to fit on my shelf. So I cut the top off, ensuring all the cereal still fits within the bounds of the box. This really highlighted how redundantly large the box is.
I reduced the height from about 330 mm to 240 mm: making the box just three-quarters of its original size.
Lorries are driving around carrying cereal boxes that are a quarter filled with air. Terrible.
(Obviously there’s way more air in the box than that, but you wouldn’t want to crush the cereals to dust.)