One who drinks a Revi'it – an amount of approximately 3 oz. – of wine recites afterwards the Beracha Acharona of "Al Ha'gefen Ve'al Peri Ha'gefen." After drinking this quantity of water, one recites the Beracha of "Borei Nefashot." The question arises regarding the proper procedure after drinking both a Revi'it of wine and a Revi'it of water. Must one recite both "Al Ha'gefen" and "Borei Nefashot," or does the "Al Ha'gefen" recited over the wine fulfill as well the obligation vis-ŕ-vis the water?
The Shulchan Aruch (208:16) rules that in such a case one recites only "Al Ha'gefen," as this Beracha covers both the wine and the water. Just as one who recites "Borei Peri Ha'gefen" before drinking wine would then not recite the Beracha of "She'ha'kol" if he wants to drink water, so does the Beracha Acharona of "Al Ha'gefen" exempt one from the recitation of "Borei Nefashot." Thus, one who does recite "Borei Nefashot" in such a case has violated the transgression of reciting a Beracha Le'vatala – a purposeless blessing. It should be noted that this applies regardless of the sequence in which one drank. Even if a person first drinks water before drinking wine, such that he incurred an obligation to recite "Borei Nefashot" before becoming obligated in "Al Ha'gefen," his recitation of "Al Ha'gefen" nevertheless absolves him of his obligation of "Borei Nefashot."
This applies, however, only if one drank a Revi'it of wine and a Revi'it of water. If one drank a Revi'it of water and less than a Revi'it of wine – e.g., he drank 3 oz. of water but only 2 oz. of wine – then he recites "Borei Nefashot" and not "Al Ha'gefen." Since he did not drink wine in a quantity that obligates him to recite "Al Ha'gefen," he must recite "Borei Nefashot" because of the Revi'it of water that he drank.
Summary: One who drank both a Revi'it of wine and a Revi'it of water recites only "Al Ha'gefen," and not "Borei Nefashot." If one drank less than a Revi'it of wine and a full Revi'it of water, he recites only "Borei Nefashot."
