Did You Know (167)

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.