Rice water has Vitamin B1. I have tried both rice water and Garlic, both works well in inducing new root. Commenting more on garlic, I will like to add here that any plant material that has a potential to develop a new plant, like potatoes, ginger, onion and garlic and leaf of plants like aloe vera has the Phyto hormones and ingredients to induce new root formation. In Southeast Asia it has been used traditionally and extensively to induce new root formation. Not only that garlic is used to break node dormancy also.
So many plant extracts have biostimulant properties, either though nutrition or unique organic molecules.
Kelp, algae, aloe vera, coconut water, ginger, garlic, licorice, tea (Camelia sinensis), soybean all have some sort of published research behind their use.