Two spring to mind. I could rant forever about them but I'll try to keep it short.

First was an apprenticeship at a furniture logistics company. I was essentially an extremely overworked and underpaid spreadsheet monkey (I got paid £4 an hour). I received no training and gained no valuable experience or qualifications. In hindsight it's clear to me the company just wanted cheap labour from vulnerable teenagers.

After this I took a job handing out leaflets for a store which buys/sells goods. The job was in fact not to hand out leaflets like I thought but to harass people I saw walking towards CEX (to try and convince them to sell their games/consoles to us instead of CEX). Obviously this was seedy as hell and embarrassing. I'd get told off at the end of the day every day for not bringing in multiple PS4s or whatever.