Basic soap and water should work. If you feel the need to occasionally “freshen up” there are some commercial products (Tucks, Charmine and others) that can be found in most pharmacies or supermarkets. However, most are not biodegradable and would need to be packed out.
You will never eliminate bacteria from this area of the body only reduce the numbers for a very short time. Keep in mind, that in terms of pure numbers, there are far more bacterial organisms in and on your body then there are human cells. Most bacteria with which we are colonized are beneficial. Many produce vitamins, aid in digestion and act to prevent harmful bacterial from setting up shop, by out competing them for space and nutrients or by producing chemicals, which prevent the harmful organisms from becoming established.
Pete