In a bowl combine the tablespoon rice vinegar, minced fresh ginger, 1/2 teaspoon salt and teaspoon sesame oil. Marinate the chicken in this mixture for 30 minutes. During this time soak rice noodles in warm water to cover for 10 minutes; drain and set in colander.
When you are ready to eat combine broth, garlic clove, remaining tablespoon rice vinegar and sesame oil and bring to a boil. Add soaked rice noodles and cook for 5 minutes. Remove garlic clove. Add the marinated chicken to the broth and simmer for 1 to 2 minutes or until just cooked through. Add the spinach and remove from heat when spinach is wilted. Season to taste with salt and pepper. Ladle out soup.