Does flavored seltzer need a hechsher?

Answer: Yes (cRc).

Reason: Flavors are kosher-sensitive.

Source:

• cRc: flavored seltzer requires kosher certification; “flavors are kosher-sensitive.”

Related questions:

• Does plain seltzer need a hechsher? No (cRc).
• Does bottled water need a hechsher? No, if unflavored (Star-K, cRc).

References: cRc (askcrc.org), “Seltzer, flavored”