We rented from Sixt through Expedia. When we checked in online, I was very pleased to be offered an electric Hyundai Kona. When we checked in at the counter, the associate was helpful and efficient with the checkout process, and he upgraded us to an electric Kia Niro (they are very similar).
He also gave us the Sixt branded "plugsurfing" card to charge the vehicle. Although I speak some Dutch, I asked him to help me set it up. When we searched for the app in the Apple App Store, the only result was ChargePoint. At this point, he became flustered and asked another employee in the back office to assist. She was even less well-informed and felt that we were set.
That was not the case, and throughout the week, we were not able to use the card (luckily a Kia dealer and my cousin with a Tesla helped keep us charged). The issue is the the Canadian App Store does not have the PlugSurfing app. I didn't realize until later that ChargePoint would help me find stations but not charge the car. Charging stations in Netherlands do not accept general credit cards for payment.
Sixt should alert their overseas customers that the app may not be available to them, and provide an alternate solution.