I can't comment on whether fasting can help with floaters but would like to issue a word of warning, particularly to those of more mature years.
In September 2012, I developed a long, dense floater in my right eye, which set alarm bells ringing because I had a detached retina in my left eye ten years previously. My doctor immediately referred me to the hospital and, after my consultation, I was told that it was an age related thing and 'nothing to worry about', just the gel shrinking etc, etc.
Roll on six months and I went for a cataract op in my left eye (brought on by the previous detachment). During the consult, I was told that they were happy to perform the procedure but only 'after I had my right eye sorted out'. It appears that I had four tears in that retina so I was booked in for laser repairs. On the day of that simple op, I was informed that there was a detachment and that I needed a longer surgery.
The question that I ask myself is, If I hadn't had to go for the cataract consult, how bad would the detachment have got while my age was blamed for the floaters?
Please don't be fobbed off with your age being used as an explanation of floaters. Yes, it can be responsible for them but you may have a leaking tear which will allow fluid to get behind the retina and cause a detachment, so any sudden increase of floaters should be a cause for concern, so do something about it immediately!
Sorry about the length of this post but it is a subject of great importance to me and our eyesight is precious - especially as we get older!