The Brisker Rav zt"l holds one who wants to
be Yotzei daytime Kiddush from another person
must drink from the wine, otherwise he is not Yotzei Kiddush.
Since the daytime Kiddush consists of only the Bracha
of Pri Hagafen, (the Pesukim we say before are not really
part of Kiddush) therefore by merely answering Amen
on the Pri Hagafen which is done during the weekdays as
well, he is not Yotzei.
Harav Yosef S. Elyashiv zt"l argues and holds one is Yotzei
Bedieved even when not drinking from the wine.