There is a an example available at https://spark.laravel.com/docs/1.0/available-variables#adding-custom-properties
which works great for adding data across to be available across all views.
If the data does not need to be or should not included in all views though please take a look at my PR: https://github.com/laravel/spark/pull/88 as I think this is a cleaner way to handle it although this is not the default way.