@Kristóf Nalesnyik If you are looking for any tools or from the Azure portal to view all the cache keys with their respective values then it is not possible.
The only way to retrieve the values is using policy. You can refer to Get value from cache document how you can retrieve the value.
The workaround will be to create a new API with different cache policies to retrieve the individual cache values and utilize this API in your code/custom tool.