How can I remove the odor from my washing machine?

I had a washing machine that we used for about six years and now whenever it was working, it smelled like the sewage. I had asked my husband to guide to outlet hose to the sink so that the water could flow out smoothly and pour bottles of odor remover into the washing machine to let it run a full cycle twice. However, the smell was still there. Does anyone know how to fix the problem? thank you in advance.