By 'using [CDT|EDT]', I meant 'adhering to a belief in [CDT|EDT] that predates drinking the soda.' If you're the only one (or one of the only ones) doing this, screening off would apply, right? But if others are doing this, there would be fewer correct predictions. And if you aren't doing this, you'll switch to CDT if you get CS, making your reasoning today for naught.

(Doing decsion theory logically enough to overcome your subconscious desires would have the same effect as sticking to your pre-soda beliefs--either way you get an ice cream choice independent of your soda)