Yes, if there is an HSN code available for the item, you must mention the same while registering for GST. If you haven't included it already, you can do it now.
You must levy the same GST on the food (dinner/lunch/breakfast/chocolate/water) as the standard GST rate applicable on these items. As of the services (room service/ restaurant service) as the normal standard gst rate on restaurant services will be applicable. For more queries and doubts related to GST you can visit GSTForumindia.in and ask your question freely.