It stored isopropyl alcohol? Well, I guess it's pretty darn clean inside, then.
If it were mine, I'd air it out for a week or so and then stick my head inside to see if I could smell anything funky. Then I'd use it to store some 2-row. And then make some beer with it and then give that beer to someone I'm not too fond of and see if they die or grow any extra limbs. And if they don't, then I'd use it without worry.