Can Vex apathic ability stun tokens?

Yes, Vex, Apathetic can stun unit tokens, but only if the effect that creates them explicitly uses the word "play" in its text.

According to RiftJudge FAQs #8758 and #9485, the distinction depends on the wording of the card effect:

• Tokens created via "play": If a card instructs you to "play a [token name]," this satisfies Vex's trigger condition ("When an opponent plays a unit"), and the token will be stunned. Examples include Reflection tokens (created by Mirror Image) or Sprite tokens, provided their creation text uses the word "play."
• Tokens created via "create" or "put onto the battlefield": If a card effect simply "creates" a token or "puts it onto the battlefield" without using the word "play," it does not trigger Vex, Apathetic's ability, and the token will not be stunned.

As clarified in RiftJudge FAQ #9625, Vex's ability uses programmatic selection rather than targeting, meaning it will successfully stun these tokens even if they possess protections against being chosen by enemy spells or abilities.