About ten years ago, I tried being a fruitarian and it certainly didn't work for me. The initial weeks were great, but after about three months, I started having problems with a high heart rate, high blood pressure and feeling nervous all the time. Surely, after three months, those can't be detox symptoms? Moreover, I have also done a number of water fasts, some of them lasting for several weeks, and I have never had any significant detox symptoms to speak of while doing those.
Personally, I am convinced that being a fruitarian is indeed not for everyone and that it depends greatly on your metabolic type whether you will do good on fruit or not. The message below in the Candida Support Forum talks about being a slow or a fast oxider and how you can test this by taking niacin (vitamin B3) on an empty stomach. According to that test, I am a fast oxidizer, i.e. not doing well on fruits.