5 days was the maximum, when I first lived on my own I didn't budget very well. I had to drink water for the whole duration. It did teach my one lesson though.. I'd never ever want to be in that state again. I think I tried to make flat bread with water and flour, this ended up in a cardboard like thing.. I did eat in on the 3rd day.
Thankfully I didn't do much besides going to college and evening work. When I got paid on that Friday I ordered a pizza and wedges from Papa Johns I couldn't even eat more than 2 slices, I threw up and felt horrible, I thought I was going to pass out. I left it for a few hours, then ate it again. Was the best pizza I ever had..
You start noticing some strange stuff when you don't eat. I think if your reasonably chubby you can go for a year without food, as long as you have vitamins etc. This was a study that was highlighted on a BBC horizon on body weight. So don't try it!