If you want a quick solution that is easily reusable, and can work for all your fluids (Gas, Windshield fluid, ect.) try using a water pistol.
Just fill the pistol with whatever fluid you need, and point the nozzle right into whatever spout your car might have, no matter how difficult it is to reach.
While it depends on what you have to hand, I'd recommend a smaller, more handheld model for easy portability and manoeuvrability for those hard to reach spouts.