I am on my longest fast to date, I am on my 7th day, and I know that if I tried to do anything like what you describe, well I don't think I could do it. I am fortunate enough to be in a position right now where nothing that I need to do requires a lot of strain. Yesterday, my sixth day, I felt the worse I have probably felt this whole time. I felt almost like I had the flu, I felt emotional, I was so tired but today I feel pretty good. I woke up after only three hours of sleep but I feel like I got all I needed. I have been dizzy since about day four, so I just do everything really slow. I'm sure it is no fun to black out!
It can be frustrating, so much to do but I think it will end up being more valuable to just enjoy my little respite.