Perhaps a good compromise would be hexagonal bottles. You can pack them just as efficiently, but they have a lower ratio of surface area to volume. From a mark

Perhaps a good compromise would be hexagonal bottles. You can pack them just as efficiently, but they have a lower ratio of surface area to volume. From a marketing perspective, you could make a new flavor and call it Hexa-Cola. I'd try it just for the name and hexagonal bottle. (If you think that's a silly reason to drink a particular beverage, then consider this: the name is probably the only reason people drink Tentacle Grape soda. Names matter when flavors are so similar.)