The F sharp dominant sharp ninth chord is a 5-note chord consisting of the notes F#, A#, C#, E and G##.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as F#7#9.
Chords that are a subset of F#7#9. These contain less notes but all of them are included in F#7#9.
In case you prefer a non-interactive variant of the chord chart, we've embedded a PNG image below that shows the notes for the the F#7#9 chord. Feel free to save or share the image as needed.