Make sure that the cable is indeed broken. A similar thing happened to me, the bonnet would not open, but the cable was not broken, the lifts that keep the bonnet open and that help it pop-up were worn out. These lifts resemble small shock absorbers and are at each side to the rear of the bonnet.
Do an experiment, with one person pulling on the lever while inside the car, have another person try to lift the bonnet. What could be happening is that the catches for the bonnet are releasing but there is not enough force to pop the bonnet up. So when someone pulls the lever inside, the catches are released and someone in the front is able to open it.
If the cable is indeed broken, I am sure that a dealer can get inside and open it and replace it for you. Just do not drive the car, as you say it is low on water, and have it towed to the dealer. If you can look from underneath and see if you can see a piece of cable hanging from the front of the car, I doubt it , but try. The cable runs along the top of the edge of the front of the car, then it disappears into the metal work. Not easy to trace.