This is the same with gas cars. It's very frustrating because they're directly being dicks to their customers. You have 3 options
1. Bring it back with a full tank of gas (annoying, as you have find a gas station and plan time)
2. Pay up front for a full tank of gas and 1.5x to 2x the price of normal gas. Now you'll be trying to drive it extra so you can use all the gas you paid for but not so much that you run out.
3. Bring it back not full and then they charge you even more.
It's infuriating how adversarial it is and I'm surprised no company advertises they don't do this to their customers. No idea if there are good ones out there but have never been to one.