Siman 172

If one forgot and placed food into his mouth without a blessing: if it is something that becomes repulsive when one spits it out, he moves it to one side and recites the blessing. If it is something that does not become repulsive, he should spit it out and recite the blessing. And why is it not sufficient to move it to one side in his mouth and recite the blessing? Because it is said, "Let my mouth be filled with Your praise," yet after the fact, if he moved it to one side and recited the blessing—his blessing is a blessing. If he did not remember until after he ate and it descended into his intestines, he does not recite the blessing, as was written in siman 167, for since it was deferred, it is deferred. He should recite only the final blessing when there is a kezayit, and this is regarding food.

But if he forgot and placed liquids into his mouth without a blessing, even though he has not yet swallowed them—he swallows them and does not recite a first blessing over them, for since they entered his mouth they have lost the status of liquids, as they are not fit for any person and are like foods after they have been swallowed, and since it was deferred, it remains deferred, and he recites only a last blessing when there is the required amount. And so it is implied from the wording of the Rambam in chapter 8, who wrote: "He swallows them and recites a blessing over them at the end." Thus far his words; meaning, a last blessing. However, our teacher, the Rema, wrote that there are those who say he recites a blessing over them, and so it appears to be the primary view. Thus far his words. And this is the opinion of the Rosh, who wrote that it is not comparable to foods after swallowing, for here, since they are still in his mouth, it is similar to "immediately prior to their performance." And they also interpret the words of the Rambam that this was his intention, meaning that he recites over them at the end the first blessing, but it does not imply so (Kesef Mishneh). And what is more correct is as the Ra'avad wrote there, that if he has no other liquids and is compelled to this—he should swallow without a blessing, but if he has others or is not compelled to this, it is better that he spit it out and not swallow without a blessing. And so the Acharonim agreed, for according to the opinion of our teacher, the Rema, it requires further study how he should act regarding the last blessing, for we have not found two blessings adjacent to one another among the blessings of enjoyment without an interruption of something between them. Nevertheless, according to his words, regarding the seven species he should recite a last blessing, for it is from the Torah (see Magen Avraham, subsection 3).