I fasted for 6 days, it's the longer I've done. I would like to fast once a year for 7-10 days and do periodic fasts during the rest of the year of 2-3 days (more or less once or twice a month) to clean my system and keep my weight.
It's very important what you eat before and after the fasting. I've read that the number of days you fast, the same number of days it's necesary to keep a light diet, specially on veggies and fruits.
I drink Urine only when I am fasting and 2 or 3 days after, and sometimes, i'm not constant, but I definitly stop it everytime I eat read meat, or spicy food which I like very much but I try to avoid because the problem I had in my colon.