This is a tricky situation for me.
Sometimes I do, sometimes I don't. ANY of my employers sans Wendy's in high school, I'd be fired immediately if they knew I was working high. So, in the big scheme of things, a risk I shouldn't take.
At Wendy's, I used to close the store, it was somewhat expected if you worked at Wendy's to smoke weed, and many of my first interactions with it were here. I'd get intermittently high throughout the day, and prior to coming in, but once 10 o clock came around, me and the other guy would go in his car and just box the shit out of it while our manager was inside. If a car came through, I'd often just take their order from inside my buddies car while smoking, and then rush inside and try to remember it all to put in the computer. Fun times
I used to work an assembly line, packaging up stuff.....either taking it from the line into the packages, or taking those packages and putting them into boxes. 8-12 hour shifts, with 2-3 hours of work at a time before a mandated 15-30 minute break. I'd get high prior to work, and I'd get high during my breaks. Was stupid as I just was running out to my car, smoking quickly, and then going into the cig shack. I'm sure other employee's knew, they just didn't care.
Very boring and monotonous work.
I got a job doing security at an engineering company my mother worked for. First day, I went in high to set precedent and so I wouldn't appear "off" and I smoked before that job the entire time. Smoked a lot during the job too when I was "on tour" checking other buildings. Actually, had it pretty good too. I worked Sunday which was a day I could get blasted, up until Wednesday, with my Wednesday shift being a day shift into an overnight. So, at the end of my first shift, I'd go get stoned and get dinner, made my 2nd shift fly by getting high every 2 hours while on tour.
Actually fucked up a good thing to be honest, as my buddy needed a job, so I got him in. We started getting more wreckless, and then his buddy (who also dealt) needed a job so we got him in, and we got more wreckless. When those two worked together, they were not smart about it at all, and it led to us all getting randomly drug tested....I called off work that day and lucked out, but they still fired me (I won the case and got a bunch of unemployment, they really screwed up their Reason for Termination on my firing sheet)
Now, I do technician/sales/engineering work. I absolutely never get high before I go out on site or meet with customers. If I'm doing lots of sales calls, I typically won't either as it makes me sloppy and I talk too de-energized, but sometimes it has the opposite effect.
But if I'm doing programming, or for instance, today I was setting up lots of quotes, I got high on my lunchbreak. I live a stones throw away from my office, so its no big thing to "go have lunch at home" and vape a bit. I've not been doing it much lately, as I agree when I'm on the clock I shouldn't be high, and I work more effectively sober on actual tasks, but anything that is a "BS" task or somewhat monotonous, I do try to get high prior.