Union station is pretty big and with all the construction and someone unfamiliar with it, it can be a bit tough finding the food section. I was really confused as I was near the car rental counters and for a moment I thought... are all the food shops closed because of the construction? Head towards the lower ground floor and the most eastern part of the station - there you will find tons of fast food places. I had a flight out of Toronto Island airport and figured it would be better to grab something from the station rather than chancing what little they had at the airport (not all airports can be like T5 at LHR!).
The sushi here is so awesome coming from a train station! I was surprised how cheap it was but I am coming from the UK. I picked up a variety roll box and a shrimp tempura roll and it was so good! If I had more time and space in my stomach I would've loved to try some of the other things like sushi pizza! Later I realised this place was a chain and can find it all over Canada but regardless, awesome place for sushi... esp on the go.