I am sure that Dr Bronner does indeed recommend lemon and enemas, but from the book I have he doesn't appear to recommend it at all.
This of course doesn't make him correct in his opinion.
The most experienced body of people with fasting since the mid 1850's to date have been Natural Hygienic Doctors in the care of the sick, and they have all agreed that enemas are superfluous, with the addition of causing enervation and debility in patients.
The body will burn any state of toxemia as fuel on a water fast, including plaque from the colon and even plaque from the arteries, by a process known as Autolysis and full ketosis. This is achieved only thru partaking of water according to thirst while fasting.
Lemon juice or any other form of "fasting" is really just dieting which supplies very limited nutrition and has been described as a starvation diet.
Drinking lemon juice or the addition of lemon juice to water while Water Fasting
will not allow the body to achieve the full state of ketosis, and therefore the benefits are severely reduced.
I thought it best to point out your options here, and ultimately allow you to make a more informed choice and decision.