odjedanput

1. suddenly; all of a sudden
   Odjedanput je nestalo struje u celoj zgradi. — Suddenly the power went out in the whole building.
   Odjedanput se setio da je zaboravio ključeve. — All of a sudden he remembered he'd forgotten his keys.
2. at once; in one go
   Ne mogu sve da uradim odjedanput. — I can't do everything at once.
   Popio je ceo sok odjedanput. — He drank all the juice in one go.

The variant "odjednom" is more frequent and has the same meanings.