Step 11: Use concentrate juices
This is mostly the case if the juice you would otherwise buy is from already reconstituted concentrate. That is the case with most of the juices in the grocery store. It is more efficient to transport concentrate juice from the orchard to the bottling plant, for example, since they can fit more on the same truck. On the same token, more cans of frozen concentrate fit on a truck from the plant to the grocery store, so the unit-cost on concentrate juices in terms of carbon emissions is lower.
Even better, buy fresh, never-concentrated juice, especially the sort that is local.