> A thick desire is one that changes you in the process of pursuing it.
>
> A thin desire is one that doesn't.
>
> ...
>
> The person who checks their notifications is [a thin desire],
> afterward, exactly the same person who wanted to check their
> notifications five minutes ago.
[I added the brackets]The author, I think, would label the desire for sugary drinks as a thin desire. However, that desire tends towards unfavorable consequences: mood swings, poor dental hygiene, weight gain. Thus it undermines one's body. This "changes you" -- for the worse, yielding a contradiction. If the preceding logical analysis is sound, the article's terms or argument are flawed.
You said it yourself - "sugary drinks... tend towards unfavorable consequences". The change happens as the outcome of the desire, not "in the process of the pursuing it".
The wording was very careful to say the pursuit of the desire changes you. That's very different than obtaining the desire changing you.
It's not a real remedy for your comment because we could probably come up with an example where the pursuit of the desire changes you in a bad way. For example, if you're a heroin addict and you're breaking into homes to steal things so that you can buy drugs. But I think it does help narrow the scope enough that the intent behind the statement becomes more clear.