Q. If the chupa is at night well after tzeis do they (chosson- kallah) still have to fast?

A. Poiskim disagree whether the chosson- kallah have to continue fasting after the day’s end or they can eat before the chupa. Those who sponsor the view that the fast’s reason is to avoid inebriation during the ceremony, would rule to keep on fasting until after the kidushin (Aruch Hashulchan E.H. 61: 21). But for those Poiskim who maintain that the fasting is for the forgiveness of sins, it would suffice to complete the day’s fast.(Chochmas Odom 115: 2 et. al.).

Horav Shlomo Miller’s Shlit’a opinion, echoes that of other Poiskim who maintain that when needed you can eat (but not drink alcoholic beverages) after tzeis hakochavim.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a