The body isn't saying it wants soda. There is no drive from the body for soda. The body might want sugar, but it's also saying it's having too much. The brain is saying it likes the taste of soda, but taste isn't nutrition.

Most people have not trained themselves to pull off intuitive eating and thus their bodies just crave fats and carbs, so the best thing to do to improve their diet is to satisfy those cravings while consuming fewer calories.

The best thing to do to improve their diet is to improve their diet. The point is to learn that those cravings aren't right, so you can learn to identify your body's real cravings are. If you keep drinking diet soda you may be less likely to make meaningful change, at best you're delaying it.