Make your hamster some hamster-safe treats.,
Change the cage layout each week.
There are safe treat recipes found on wikiHow, YouTube and in a big book called Happy Hamster (a cookbook for hamsters with hamster-safe recipes).
Place treats inside toilet tube rolls. This provides enrichment as the hamster needs to find the food, climb inside, then maybe even roll around a bit. Or, make it harder by closing down the ends, so that your hamster has to work harder to get at the treat. Expect the toilet roll to be destroyed; remove once the treat has been consumed.
, This will give the hamster new exploring options and it makes cleaning out the cage more entertaining for you too.
If possible, buy your hamster a bigger cage 360 square footage plus. Hamsters with bigger cages live longer and are happier and healthier.