すみません、このスープは魚のだしを使っていますか？ — Excuse me, does this soup use fish stock (dashi)? (Restaurant · Dietary · Restriction, Formal — to staff, JLPT N3)

Gesture & etiquette

Point to the soup on the menu or the actual soup, then make a questioning gesture.

Be polite and understand that not all restaurants can accommodate complex dietary needs, especially small local ones. Have backup phrases for 'no meat', 'no fish', etc.