The trick that has worked VERY well on my cages is vinegar and hydrogen peroxide. If the hydrogen peroxide isn't available, the vinegar does seem to work pretty well on its own. I've found this has so far also helped prevent the white build up that comes with years of use! When cleaning cages and cage accessories (such as litter boxes), I just spray it down real good with vinegar (typically use white vinegar, since that's most readily available), concentrating more spray on the nastiest spots, then hose it off. Everything washes away pretty well and the odor seems to be minimized!