Coffee enemas are good in some situations related to detox.

Caffeine from the enema is absorbed into what is called the "entero-hepatic system" and delivered directly to the liver. This is an especially efficient and fast way to get coffee to the liver. This coffee stimulates the liver ducts causing them to empty into the colon enabling the liver to detox more efficiently.

Also, in more depth (from the web)...

"The alkaloids in the caffeine stimulate the production of an enzyme called "glutathione-S-transferase", which is an enzyme that facilitates the liver detoxification pathways. The coffee enema is safe even for people who are sensitive to caffeine because the coffee remains in the sigmoid colon, where it will not be absorbed, provided the proper amount is used and the enema bag is not placed too high."

The downside of drinking coffee is that coffee facilitates the transfer of mercury through certain cell walls enhancing its ability to damage cells, so mercury toxic people should avoid coffee orally.