How do I drain bad gas from a 2014 Subaru Forester?

Hmm.... Are you sure it's bad fuel? Before chasing a messy drain I'd try filling up with premium and adding a bottle of Techron to see if you can balance it out and get through it. There's a small chance you sucked up water from a near-empty tank if you're used to running ow before refueling. Try to always refill before the 2-gal warning light comes on. Good luck. Ern

You will need to drop the tank. This is best done by a mechanic.