How to get member Access Expiration?

When exporting Audience using CSV format, there’s a field called “Access Expiration” which confirm until when the member should have access to their tiers rewards.

How can I get such field through the campaigns/{id}/members api endpoint?

You can request the pledge information as an include in the membership info and then check the pledge details. However you shouldnt need to do that if you are going to check for the user’s access to your local rewards - currently_entitled_tiers and currently_entitled_amount_cents will always show what a user is entitled to at any given point. If those two dont show a tier and a $ amount (in your campaign currency), then the user is not entitled to a tier or a $ amount reward.