If I counted jobs I had while in school you're probably looking at a couple of 1-2 day positions. But I don't count those as part of my "real world" experience.
Up until this year, my shortest tenure was 2 weeks, where I went to work for a friend whose small company had been contracted out to work for an international Canadian bank. I'd actually left a decent paying job to work with him, since he was supposed to place me in a client-facing (in this case, the bank) position with little-to-no programming. I'd just started learning Java, but at that point it was more to increase my knowledge than for any reasonable practical usage.
In any case, I got thrown into a near-full on programming position where I was not given any training and given things to look at that I'd no idea what was going on (again, bear in mind I'd effectively zero experience with Java). A week in, they told me that "they were not impressed with my performance". I told them that at this point they'd not given me the tools or help I needed to succeed. A week after that, they fired me. And I am no longer on speaking terms with my former friend. And yes, I'm still bitter about the experience.
Anyway, that was the shortest job I'd had until this year. I got hired for a work-from-home position, and I started work in mid-March. Unlike the story above, my onboard experience was smooth, I got to have virtual interactions with the entire team, and started to take on work by the end of the week.
And then Ontario got shut down thanks to the Pandemic. The company's clients were mostly retail outlets, and with those shut down, they needed to streamline. And any way you slice it, it's a pretty easy call to cut the guy with 1 week of experience.
Unlike the story above, there's no bitterness here. I am saddened that I didn't get to continue there, but it is what it is.
And now I'm onto my third company in 2020. Hopefully I can stay on with this one.