I adapted this recipe but will post a link to the original. I have to say that it has out performed shop bought items every time. Our dishwasher smells clean and fresh and our dishes don’t smell at all.
8 parts bicarbonate of soda.
3 parts citric acid
Tea tree and\or eucalyptus oil to scent.
Add and mix into a coarse powder. Add 1 TSP to each load