I've been giving this some serious consideration i'm thinking starting Dec 1 i want to try a water fast for 15+ Days drinking only water no calories

I've done some research and the health benefits are amazing along with mental clarity.

At night i'm thinking of drinking a tablespoon of organic apple cider vinegar

Don't do it. If you want fasting, try intermittent 8:16 fasting.

Prolonged fasting is just going to make you lose the wrong kind of weight (not fat).

It's a stupid concept that has no merit other than very mild changes to autophagy, blood pressure, etc. The downsides FAAAAAAR outweight the good sides.

My main concern is to feel mentally and physically healthier not to lose weight. I'm not overweight small amount of fat.

5'8 140 lbs, have you done intermittent fasting yourself?

Yes and it's also a lot more properly researched than prolonged fasting (due to obvious health risks).

You won't be feeling physically better from a prolonged fast. Mentally, I can't really know. Physically definitely not.

If you're doing this as a kind of challenge to yourself or for meditative reasons or whatnot, then whatever floats your boat. You won't die from this and unless you do it frequently, there shouldn't be long lasting effects (other than a massively slowed down metabolism, but you can recover from that).

this guy is worse than raynor

What do you mean? No clue who raynor is

Someone cal is jealous of

Did it for 3 days earlier this year. Ate a whole Honey dew melon after, tasted better than pussy.

Doubtful.