Instead of buying rusk off the shelves, which often contains undesired amount of sugar and other additives, why not make your own? It’s easier than you thought and much cheaper!
Bread (even if a few days old, it’s ok)
Cut bread into sticks of appropriate size.
Bake in oven on the lowest temperature setting for at least 1 – 1½ hours. It should be hard but not burnt. Turn over after 30-45 minutes, if necessary.
Store in airtight container.
If you don’t toast the bread long enough, it will become soft easily. If the bread is toasted long enough, it will remain hard even if you leave it out in the open.