# For as you

The word "you" is plural and probably refers to the people of Judah

# as you have drunk

"as you have drunk suffering" or "as I have punished you" 

# my holy mountain

This was a way of referring to Jerusalem.

# so will all the nations drink continually

"so all the nations will drink in suffering continually" or "so I will punish all of the nations without stopping" 

# They will drink and swallow and it will be as though they had never existed

"They will drink in my punishment fully until they cease to exist" or "I will continue to punish them fully until I completely destroy them"