Maintaining Consistency for a Blessing in Casual Drinking

I drink coffee at work, and next to me sits a friend who also drinks coffee. Is it permissible for me to step outside for a few minutes if my friend maintains the consistency for a blessing for me?

 Since you are not eating or drinking together consistently, but rather coincidentally both drinking coffee, and you have no obligation to return to the place of drinking coffee because of the friend. Therefore, when you return to your place and wish to drink, you need to recite the first blessing again.

Talmud Pesachim, page 101, side 2: "Rav Chisda sat and said in his own name: what you said, that a change of place requires a blessing - this is only said regarding things that do not require a blessing after them in their place, but things that require a blessing after them in their place - do not require a blessing. Why - because it returns to the first consistency. And Rav Sheshet said: both this and that require a blessing."

And on page 102, side 1: "Friends who were sitting together and got up to go to the synagogue or the study hall, when they go out - they do not require a blessing retroactively, and when they return - they do not require a blessing initially, Rabbi Yehuda said: what are we talking about - when they left some friends there, but if they did not leave some friends there, when they go out - they require a blessing retroactively, and when they return - they require a blessing initially." And see in the Talmud the resolution of the baraita according to the views of Rav Chisda and Rav Sheshet.

Nevertheless, according to Rav Chisda's opinion regarding bread (and according to the Mishnah Berurah even regarding things that require the "Me'ein Shalosh" blessing), since if he left his place, he must return to his place to bless, therefore when he left the place of the meal's consistency, he did not completely detach from his first meal place, and therefore if he wants to continue eating, he does not need a blessing. And so ruled the Rema in Siman 178. However, the Shulchan Aruch rules according to Rav Sheshet's opinion that both in this and that case a blessing is required. (And they further dispute, that according to the Rema only the first blessing is needed. And according to the Shulchan Aruch both the first and last blessings are needed)

And even according to the Shulchan Aruch, if he left some friends, since he must return to his first place, he did not detach from his place of consistency. And the later authorities dispute whether leaving some friends helps regarding bread or not, the opinion of the Taz is that Rabbi Yehuda's words that leaving some friends helps is only regarding bread, however, the Magen Avraham, the Gra, and the Eliyah Rabbah, and so ruled the Mishnah Berurah in Siman 178, Sif Katan 18, that leaving some friends helps not to bless again when going out.

And behold, the entire law of leaving some friends is because there are still those who eat, the place of consistency was not detached. But when two sit next to each other, it certainly does not help, and when he goes out and returns and wants to continue drinking, he recites the first blessing.