I think it depends on your job and how physically demanding it is. I fasted for 21 days during Lent and worked full-time the entire time without a problem. However I have a desk job that doesn’t require heavy lifting or being on my feet and I did not exercise during my fast. Mostly just went to work and went home and read a book and went to bed.
Mixing 1/4 tsp of salt in with your water may help your symptoms. I’m not diabetic, but did experience those symptoms when I only drank water. The next time when I mixed the salt in those symptoms went away completely.