Battle of the Bottles

A major soft drink manufacturer decided that providing choices in the
container size in the six-packs of its beverages might help move the
product off the shelves. The unique selling idea was to have several
different container sizes in the very same six-pack.

One of the most successful packages comprised two 250 ml bottles, two
500 ml bottles, and two 1000 ml bottles. To the bottler's surprise,
after purchasing the beverage, most people chose to drink from the
1000 ml container first. Postmarketing research showed why: It was
the liter of the pack.