300. Bentching Over a Cup
44:18 If there is an idolater present during bentching, the text recited in the HaRachaman section is “osanu, b’nei bris, kulanu yachad,” that God should bless those who are members of His covenant.
45:1 If three men ate bread together, they must join together to recite bentching with a “zimmun” (literally, an invitation; that is, a call to bentch). There is a mitzvah to recite bentching over a cup. This should optimally be a cup of wine but one might also use beer or liquor if they are considered typical local substitutes. Some authorities say that bentching should be recited over a cup even when bentching alone. Those who are meticulous in their mitzvah observance will not hold the cup when bentching alone; instead, they will place it on the table in front of them.