Yeah it will stop working if someone will drink my brake fluid
still doesn't make any sense what you are trying to say. Maybe ABS or a brake assist can stop working properly which i don't think but still in any situation you will still have your foot. 12v battery doesn't make your brake pedal to drop dead. Btw my leaf does not have a brake assist it would be a nice feature to add. Your brakes will work even if you will half strip your car and remove any batteries from it. As long as the brake lines ar fine. It will work.
Starting with the MY2013 LEAFs, Nissan switched to a mechanical accumulator to assist with braking force. (And, yes, ALL LEAFs have some method to assist with the braking force needed to stop the car since doing that with just your foot with four disc brakes is quite difficult.) But in the MY2011s and 2012, there was a 12-V ultracapacitor to assist with braking force. If that ultracapacitor was not fully charged to nearly 12V, the vehicle would COMPLETELY lose the brake pedal and it would move all the way to the floor with little effort. Low voltage could be caused by a low battery or you could have a fully-charged battery, but the capacitor was discharged for service.
The latter case happened to me. I took my LEAF in for a service bulletin to reprogram the braking computer. They completed the service in about an hour but the would not return the vehicle to me because they said it had no brakes. I asked what they meant by "no brakes" and they said there was no pedal. The guy sat in the car pushed the pedal all the way to the floor with ease. They gave me a loaner car for the weekend and the ultracapacitor had recharged by Monday and all was well.
Since that time I have been diligent to keep the 12-V battery fully charged.
I believe the MY2013-2017 LEAFs cannot have the problem mine had due to the ultracapacitor, but I suspect they can still have the same issue due to a low battery voltage since it appears to result in communications issues with the braking computer over the CAN bus.