In Star Wars: The Last Jedi, the Rebel cruiser runs low on fuel. What kind of fuel are they using?
Probably Rhydonium. Its explored at much greater length in both animated TV shows. But basically its a volatile fuel found on the planet Abafar that can power starships. We don't really have many details beyond this in canon.
To be clear, this is different from the hypermatter that powers hyperdrives. Though they were low on that too.