3 days (2 training, 1 work). It was a commission job, being one of those annoying people in the shopping malls who stop you and try to sell you stuff. I earnt $20 which didn't even cover the cost of travel / lunch for the days. Decided I'm not going to pay to go to work because that's stupid.
There were two jobs that share this short duration.
Technically one was only 3 days... but they were spread out during a month. (It was an on-call job so if I didn't hear from the boss by a certain time then there was no work the next day for me. Ended up being like one day, a week off, one day, 2 weeks off... final day.)