I worked at UPS for a bit over a year at one of their largest facilities, at that location you were split into 1 of 3 roles: sorter, un-loader, loader. Un-loaders just emptied trucks onto the belts making sure to keep labels facing up for the sorters, the sorters had to memorize what locations went where and place it on the correct belt depending on which sorting line it was anywhere from 4 belts to 12 belts to memorize, loaders would need to load the trucks scanning each package and verifying it went on their truck. I worked as a sorter and got an extra dollar an hour, it was not uncommon to get a bunch of boxes that weighed 50lbs that needed to each go to different belts which you would pick up from in front of you and place behind you at varying heights. Overall the union benefits are amazing, the work itself was simple but very physical, and as others have mentioned the coworkers and supervisors were terrible.
I worked in a UPS hub for a brief stint in college, the 11-3am shift (or something like that). I was primarily a loader of the long trailers that moved between hubs, which was kind of fun and good exercise. You'd have a mountain of boxes come sliding down a chute into the back of a trailer and you'd have to verify it was in the right truck (by zip code), scan it with a wrist mounted scanner, and stack/throw the boxes from floor to ceiling. It was a lot like tetris, actually. Bonus: you get to throw stuff like iMacs (this was 1998/99 or so).
If you memorized a whole bunch of zip codes you could pass a sorter's test that paid you an extra dollar or two an hour, even if no sorter positions were available. The college kids tended to migrate up to the sorting line fairly quickly. A lot of the non-college crowd wanted to end up a driver, but there was an 8 year wait list for that in the area I worked.
And yeah, the first level managers were a joke. They were just there to baby sit and power trip. They were also weirdly homogeneous. I still have a vivid memory of seeing 4 of them standing together in the same khakis, with the same haircut, and smoking the same brand of cigarettes (Marlboro lights).
I only lasted 7 weeks because my school schedule changed to include 8am classes (which is a challenge after getting home at 4) and my other 20 hour a week job was much better, but it was not a bad gig overall given my options at the time. It was very fatiguing, though. I'm not sure I would try to stack it on top of a full time job and school.
