Re: 2 week (or more) water fast. and hi, im new!
If you want a permanent fix to weight loss, you should fix your eating habits first imo. Fasting for one day and binging on junk food the next day will give you an eating disorder and make you feel bad.
The best diet in my opinion is very simple! Fruitarian, meaning you eat only one type of fruit for each meal of the day. Eat as much as you want but only of that one kind of fruit. You'll lose lots of weight and more importantly, you'll be eating well after your fast and keep all your results. With a fruitarian diet, start slow (1 fruit meal every 3 days) and increase at your own pace. Currently around 90% of my meals are fruit only. It's the best!
Also, maybe you should read a book on fasting. Whenever I see people fasting for weight only, most fasts don't work and it often goes to waste because people never bothered to fix their eating habits.
When water fasting, the only thing you should be having is distilled water (made from your own distiller). Anything else starts up the digestive system and reduces the fasting experience. That includes all vitamins and supplements.
Most people do only mild exercise at most during fasts. When fasting, most people sleep and rest a lot, which is best. The best advice is to listen to your body.
If you do choose to do some exercise (like yoga) your fast will not last as long, but that shouldn't be an issue for a 14-day fast. As well, when exercising during a fast, your body is more focused on performance and improving muscle mass rather than healing, but I guess you're not doing this for healing.
Anyway, good luck. I hope you feel better.