Alternating juice/water/water+caffeine fast

I used to fast a lot more in the past, its been a long time since I've fasted consistently. My fasts would typically be a juice fast (for 5-11 days) or a 3-4 day Water Fast or a coffee+tea+water fast for 5-6 days.

Right now I'm on day 18 of a fast(not entirely water) and I'm not sure how healthy or effective anything I am doing is. Probably total days of water only would be about 8 in this fast so far, the rest has been either a combination of random sugary drinks, or water + coffee/tea.

The way I am doing things at the moment is: Monday water/coffee/tea, Tuesday - Friday water only, sat/sun juice/tea/random sugary drinks. (I work and deal w/ customers w/ a light amount of lifting and which is what makes Water Fasts exclusively very difficult)

I have never fasted longer than 11 days in the past and I was a lot skinnier then so it was a little easier to listen to my body. Now that I'm on day 18, I feel like how I'm handling my fast is inefficient and maybe down right ineffective for detox and getting that "clear headed" feeling I used to get after 7 days. Any tips?

Secondly, I have never had this problem before. After about 10 days, I am getting extraordinarily thirsty. On an average I'm drinking 3-4 liters of water a day (on the WF days) and the next morning I still feel dry mouth and there is heavy color in my urine. I almost feel as if my body isn't absorbing water? is this normal?