Are you sure you put in gas and not diesel?
Anyway, your best bet- and I've done this with very old fuel in a tank- is to get a gas can, and get some good gas from somewhere. Fill up your 5 gallon can, and put all that in the tank if the tank will hold it. Most fuels now have ethanol built into them, so they will absorb some water. Now the car should start, but it might take a few times of cranking the engine.
Remember, every time you turn the key to start, the computer sprays a startup mixture of fuel into the engine. Repeated attempts with no success and you'll flood the engine. It will start to sound like the battery is dead suddenly cranking slower. When this happens, use the emergency start method to clean out the fuel. Key off, floor the accelerator and hold. Turn the key to start still holding the accelerator as far down as you can push it. This tells the computer not to spray fuel. Crank the engine for 15 secs or until it sputters. Turn the key off, and start normally with your foot off the accelerator. This procedure is given in your owner's manual, and works on all EFI vehicles in the same manner- basically mimicking the method of starting a flooded carbureted engine.
You might have bad fuel, you might have something unrelated. Putting in good fuel will get it running and let you know if it was bad fuel. If 5 gallons of good fuel doesn't get you running, then you need to start pretending like you don't know what happened last night and you're simply trying to diagnose why a car won't start.