Hey bud! I work on the railway. I’m on track and my duties are not always heavy. Lots of moving around then some rest, nothing too heavy to carry. For my first 5-day dry fast I’ve taken days off work because I wasn’t sure how my body would be. I can say now I’m glad that I took time off. I’ve felt pretty lethargic. If it’s your first extended fast I’d say take the time off to learn how your body is during fasting.
I broke my last fast 45hrs in because I had no energy and was getting winded easily. My situation is the same as yours I work for a utility contractor, cranes and rigging & shop work on slow days. I’m gonna try again on Wednesday, I can manage 2 days working then I’ll have the weekend to rest and do nothing maybe sick out on Monday giving me at least 5 days
You can practice on days off by waking up, no food or water, go for a 3 mile walk, then dry fast until say dinner, then drink eat. You’ll get used to work/exercise in the dry fasted state, should eventually be able to be fine at work.