Sugar is bad, mkay?
If a junky cuts his meth intake in half, would you tell him to carry on, because he's only using a little bit and that it won't hurt him?
You don't like the taste of diet pop or plain water because you are a sugar-junky. You just crave the sugar highs. Cut all those sugary drinks from your diet, keep that up for a few weeks and those sugar cravings will pass. And yes, juices are also sugary drinks...
If you keep even only one sugary drink in your daily intake, you will feed your sugar cravings. You will be craving more and more sugar during the day.