If one makes a hagofen on wine, that covers all other beverages (that are in front of him or, at least, he had them in mind when he made hagofen).
1. How much wine must one drink for this to work?
2. Does it also work by grape juice, or re-constituted grape juice (which is a machlokes if it’s shehakol or hagofen, though I personally make hagofen on it)?
He should drink at least a “melo lugmov” i.e majority of a revi’is, if he wants to cover other beverages.
Hagaon Reb Y.S. Elyashiv held that only real wine and not grape juice is important enough to cover all other beverages but his son in law Hagaon Reb Chaim Kanyevsky held that also grape juice is considered wine to cover other beverages.
O:CH 174:4 Biur Halacha ד”ה יין