From what one read about the product, "Affresh" is mainly sodium percarbonate (oxygen bleach), which in theory should deal with mould, slime and odors, will do nothing to break up the gunk and build up inside a washing machine.
For that one needs a dedicated washing machine cleaner such as "Washing Machine Magic" or the descaling/cleaner Miele sells for front loaders. The later is common enough in Europe, but hard to find on these shores.
In either event, both of the above mentioned products contains acids, surfactants and perhaps a disinfectant. Their purpose is to remove and disslove hard water deposits, soap/detergent residue, mildew, moulds, etc that are on heating elements and between the washer drums.
Depending upon the washer, one could simply bung in several quarts of white vinegar and baking soda (the chemical reaction causes foaming, which helps loosen the gunk), or simply white vinegar.
Agree with another poster that using "Tang" to clean a dishwasher or washing machine is a pretty expensive way to get the chemical one is after "citric acid", and adds lots of sugar which does nothing. Citric acid is found in most Kosher food stores/sections labled "sour salt".