Scales to Play Over F#sus4
Every chord is a subset of several scales: any scale that contains all of a chord's tones fits over it. Pick a chord to see the matching scales from its own root, the major keys the chord belongs to, and full fretboard diagrams for every scale on guitar.
A F#sus4 chord contains the notes F# – B – C#. Any scale that includes every one of those 3 tones fits over it — from the root F#, that means F# Major, F# Natural Minor, F# Melodic Minor, F# Harmonic Minor, F# Minor Pentatonic, F# Blues, F# Dorian, F# Phrygian, F# Mixolydian, F# Dorian Bebop, F# Mixolydian Bebop and F# Spanish. Start with the first scale listed: it is the most common choice, and the others color the same chord tones differently.
F#sus4 is also diatonic to 5 major keys: A major (relative minor F#m), B major (relative minor G#m), D major (relative minor Bm), E major (relative minor C#m), F# major (relative minor D#m). In a song from one of those keys you can also solo with the key's own major scale or its relative minor pentatonic across the whole progression, not just this chord.