You can just give them the way they are, hamsters love runnin through tubes, except they're a bit small if you have Syrians.
You can also cut holes in the sides that they can run through, or hide treats in them and fold the ends shut
you can also connect them to make a tube maze!
Or use hamster safe string to hang them from the roof of the cage to make hanging tunnels!
Toilet tubes are basically the perfect dwarf toy xD