I worked at Pepsi in the 80s when we were still doing glass bottles. There was an entire line of guys that stood there all day and sorted glass bottle by soda. A 24 bottle tray with random bottles was grabbed at the head of the line and as it went down the line you grabbed the bottles for your stack, Pepsi, Mt. Dew, Diet Pepsi, and so on and put them in a 24 bottle tray of just that flavor. Once you had a full pallet of trays you hit a buzzer and fork lift guy would swing by and grab that whole pallet.

This went on all day, every day. If I recall there were 5 or 6 guys on the line plus forklift guy. And life sucked if one guy was sick.

Then, once all the bottles were sorted they were all put on the bottling line and washed, sterilized and refilled with soda.

Plastic did away with a lot of jobs at the bottling plants. Maybe 20 people per plant? Then the lack of a need to wash and refill glass did away with all the "local" plants that were scattered all over the country to just a handful these days.