While not specifically mentioned as soda substitutes, some of the herbs listed above to help overcome addiction also have soothing properties. I’ve found Skullcap, Catnip, and Lemon Balm/Melissa to all be wonderful to ease my headaches and calm anxiety.
In addition to exploring herbal remedies, another suggestion could be spellwork to help banish a bad habit. @Silverbear has a spell here to help give someone move away from a habit that isn’t serving them:
Whatever you choose to do, wishing you good luck with breaking the addiction, @sara6! Blessed be 
