The two effective homemade washing machine cleaners are vinegar and baking soda. A 1/4 cup of vinegar and 1 quart of water creates a solution strong enough to tackle built-up residue in your washing machine.
Four tablespoons of baking soda dissolved in 4 cups of water works equally as well with the added benefit of getting rid of any nasty smells. A cloth soaked in either one of these solutions can be used to clean the inside of a washing machine. After doing this, put the washing machine on a rinse cycle to get rid of any trace of vinegar or baking powder.