The FHIR specification defines RDF (specifically Turtle) as one of the possible serialization formats for FHIR resources. This means that every FHIR resource or a bundle of FHIR resources can be viewed as an RDF dataset and queried using SPARQL.
I've created this tool to demonstrate how FHIR resources can be queried using SPARQL and in general, experiment with the RDF representation of FHIR resources. You can import your own FHIR resources in the NDJSON format (this overwrites the existing resources) or start with querying the example dataset.
The tool uses the rdflib.js library (published as rdflib on npm) to create a triple store in the browser and run your SPARQL queries against it. The data does not persist between sessions.