Actually I found an email correspondence with on! going back to March. All flavors are Kosher.
Hi Zyn on shabbos we’re inevitably one presses his lip on the pouch is that a problem of sechitah like sucking juice out of a gauze ? If it’s permitted can you please give a brief explanation
No problem.
First there’s no sechitah in the mouth. That’s called derech achilah. Othereise you would never be able to bite into a fruit. the case that you’re referring to is when you’re using the mouth to suck juice out of a cloth. Not that the cloth is in the mouth.
Second, even if there was sechitah inside the mouth, you would have to be intentionally trying to squeeze out the liquid. Otherwise we can combine Psik Reisha D’lo Nichah Leih (assuming it’s a פסיק רישא) with סחיטה כלאחר יד and probably one or two more צירופים.