I've fasted before, the longest I've done it is two weeks. Mainly they were tea, water and juice fasts (that is, I drink all of these on a fast, I've never done just exclusively one of these.)
I've found the first 1-2 days are the hardest, the rest of the days are easier for a while until the deep hunger starts up after 10-12 days. The only real bad thing I've ever found from these fasts is the incredible
boredom I get from not eating. I am one of those folks that eats when they are bored or restless.
To Pondering,
Be careful of doing a fast if you have diabetes or some other special condition (or taking meds) as it can affect how your body metabolizes things. If you have one of these conditions or are taking meds I'd ask a doctor first just in case, because sometimes fasting induces ketosis and it can have weird effects on your body.
Doesn't fasting always induce ketosis (water fasting, that is, or juice fasting if there isn't much juice or it is consumed infrequently)?