The minimum amount of drink that obligates reciting a bracha acharona is a revi’is (2.9 oz., 86 gram). (Some say that for wine the measure is the volume of a kazayis (about 1 oz.), and one should therefore not drink between 1 and 2.9 oz. to avoid a doubt. )
For the sips to add up to a revi’is they must be consumed within a certain timeframe. Some say that it is the same as for food – kdei achilas pras, six minutes, while others say it is a shorter timeframe of the time it takes to normally drink a revi’is, which is less then a minute. In his final ruling, the Alter Rebbe sides with the longer six-minute timeframe.
One who drinks the measurement which requires a bracha achrona should make the after bracha immediately after he concludes his drink, as if he will wait the amount of time it takes for the drink to absorb he will not be obligated anymore to recite a after bracha, for once the food drink has absorbed the obligation to recite the bracha ceases , if he did not make a after bracha right away as long as he feels satisfied that he quenched his thirst from the drink he can make a bracha achrona.
If he waited a longer amount of time and now feels thirsty he cannot make a bracha achrona, and even if it was a short amount of time if he is very thirsty he cannot make a bracha achrona this halacha is very relevant in the summer or when people are doing exercise.
If one is uncertain recent achronim set the time at a half an hour that if a half n hour passed since he drank and he isn’t sure he should not make a after bracha
If one is constantly drinking one cup after the other he is to see to it that a half an hour doesn’t pass from one drink to the next and then one can recite a bracha although a long period of time has passed from when he began to drink as every half an hour he had a drink.
If one doesn’t know how much time it will be until his next drink then what he should do is have in mind that the bracha he is making is only on what he is drinking now and conclude this drink immediately with a after bracha.
Once the drink has absorbed and one is now thirsty again the previous bracha shehakol does not work ant more and one needs to make a new bracha shehakol.
Whether the bracha extends to a new location depends on the obligation to recite the bracha acharona in the place where one ate.
If the after bracha is Borei Nefashos – One does not have to return to recite borei nefashos. Therefore as soon as he leaves his original place his meal is over and a new bracha must be recited (even if he returns to the first location).
If he has the intention when he made the bracha he may continue eating in another room in the same house. Acharonim suggest that nowadays since it is common practice to continue drinking or snacking around the house, it is assumed to be one’s intention when he made the bracha and he may continue in another room. However, outside the home he must recite a new bracha.
If in the new location it is possible to see the original spot, one is considered to not have left his place and does not recite a bracha (even from outside) One who is walking outdoors does not need to recite an additional bracha only as long as he can see his first location. (unless he is in a gated area which is like one room)..
