49:3 If wine was mixed with water, if the wine is only one part to six parts water, the wine is nullified and the drink is considered water (even if it retains a wine flavor – Mishnah Brurah 204:33). If the proportion of wine is greater than this, then if the local practice is to dilute wine to this extent for drinking instead of undiluted wine, then we say hagafen and al hagefen over it. If such is not the local practice, his personal opinion makes no matter (and he must recite shehakol).
49:4 Just like bread exempts most other foods from requiring their own blessings to be recited, wine exempts other drinks from both a blessing before and after. (He need not have the intention to exempt other beverages – Bi’ur Halacha 174:2 s.v. yayin patur.) This is only the case when the other drinks were in front of him when he said hagafen, or if he at least had the intention to drink them. If this is not the case, there is a doubt whether or not a separate bracha is required. One should therefore avoid drinking other beverages in such circumstances until after reciting al hagefen for the wine. Alternatively, one may say shehakol on some food that requires it and also have the beverage in mind.