What is the best detox method after chemotherapy?

Fluids! Chemotherapy is in your bloodstream for a fairly short period of time (less than a day) in most cases. It is broken down by your liver/kidneys into metabolites which are eliminated. Staying well-hydrated will help flush these from your body. Some heavy metals in chemo, ie platinum, can remain detectable in your body forever. A naturopath may be more helpful than I am in this regard!
Time. With time your own body will remove the chemo from the body by the kidney or liver. You just need to stay active, get good sleep, eat healthy and drink fluids adequately.