I believe quite a few people have a detox day, and I'm sure our overworked western life-style bodies benefit from it. A popular method is to chose a day (possibly a Sunday) when you're not indulging in heavy physical activity,) and just eat fruit which contain lots of liquid, such as oranges, grapes, plums, nectarines, etc. (but not bananas). Also drink plenty of liqui (fruit juice or water).
This diet might leave you feeling a little light headed if you follow it for more than one day but it should help clear out your system. (And no smoking or alcohol of course).