suddenly; all at once
La blessure ne provient pas d'une flèche mais d'un coup d'épée.
The wound was not caused by an arrow but by a sword blow.
— Aguirre, la colère de Dieu (1972)
Le son était parfait et d'un coup, il y a eu des interférences.
The sound was perfect, and then suddenly there was interference.
— Blow Out (1981)
Now, drink it in one go!
It happened all of a sudden.