2 cups baking soda
2 cups vinegar
4 cups water
Be careful when adding the baking soda, do so very slowly as it will foam up. Cap and shake gently from side to side, opening the cap to allow air to escape (you may need to do this several times). Add about 20 drops of essential oil if you want it scented. Shake side to side before each use as the baking soda will settle.
(Alternatively, you can also add vinegar to a bottle of fabric softener that is 1/4-1/3 full. It works great, and will leave your clothes with a mild softener scent. You could also use only a little bit of softener, then fill your dispenser the rest of the way with vinegar.)
I dilute it about half & half with water in my dispenser in my washer. There isn't any residue left behind. My clothes are static-free and soft.
And no, they don't smell like vinegar. I've read that vinegar actually helps rid your clothes of any detergent residue. The vinegar smell is completely gone once the clothes are dry and you've saved money (and avoided unnecessary chemicals) in the process!