The rental prices on the website don't include fuel costs.
Hirers must therefore return your vehicle with the same amount of fuel as it had at the start of the rental. You're not required to provide the vehicle with a full tank, but this does make things easier when checking the gauge at the end.
Your vehicle is required to have at least a quarter of a tank of fuel at the beginning of the rental, to get the rental started.
If the driver returns the car with a lower level of gas, you can proceed to an adjustment for classic rentals.
For Getaround Connect rentals the fuel adjustment will be done automatically if your car is compatible, find out more about Getaround Connect adjustments here.