There are a lot of cool TTC drivers on the 192 Airport Express route. There seem to be about a dozen who drive it regularly. I can't tell you how many times a driver has let someone who has just arrived from out of town - who has no $CDN or only big bills - on the bus with a promise to pay their fare upon arrival at the subway station. As long as you level with them, I'm willing to bet they'll let you on. That having been said, I'd probably keep the $2.25 in my pocket just in case you run into a grumpy one.