You can leave someone’s Sharetank anytime. Here’s how
Open Z App
Tap on Sharetank in the bottom menu
Tap on the three dots (***) in the top-right corner
Tap on the option in the menu called ‘Leave Sharetank’
Please note: By leaving someone else’s Sharetank, you’re losing access to their fuel balance. To re-gain access, you will need to re-enter the access code, and they will need to accept you again.