Not much going on at 5am, but here are a few things to consider.

Grab a shower at a nearby gym (day pass). There is a central YMCA a few blocks north of the bus terminal (two blocks N of College St). If you have meetings at 9am and have traveled all night, I suspect a shower will be a welcome start.

Timothy's, Tim Hortons, Second Cup and Starbucks are all nearby - within 2 blocks. I would recommend grabbing a bagel at one of the restaurants at Bay/College.

If the weather is nice, you can walk around Queen's Park and University, as well as the University grounds - statues and war memorials and generally not a bad place to get some fresh air.