Caveat: I've been away from TO for 10 months now, so my info may be out of date.
First, which Sheraton are you staying at? If it's the Sheraton Centre on Queen & Bay, then ask them if they have a deal with any nearby gyms whereby their hotel guests get cheapter 1-day or 1-week passes.
I believe Monster Gym is now called Fitness 365, but if you are staying at the downtown Sheraton it is pretty far away from you. If you still want to go there, their contact info is in the CityGuide I mention below.
Going on the assumption that T-Men and T-Vixens would want a squat rack and everything else is gravy, I would suggest Diesel Fitness near King & Spadina. It's a high end place, but they did have a squat rack, packs of 10 passes, and use of towels was included. Their web site is:
Epic Fitness (St Joseph Street b/w Bay and Yonge) has both a squat rack and a power rack and a place to deadlift. Their crowd is mostly gay male, however, which makes some straight guys uncomfortable. YMMV.
Go to http://www.torontolife.com
- Click on City Guides.
- Click on Health & Fitness Guide.
- Click on Full Service gyms. Out of the ones listed, the ones that can be walked to from your hotel are: Adelaide Club, the Bally Total Fitness at the Eaton Centre (I wouldn't go into Bally's if you paid me, but that's me.), Epic, Yonge St Fitness, etc. Of course, what I consider walkable may not be what someone else considers walkable, so other Torontonians should chime in here.
- Go back and click on Boutique gyms.
- Click on Diesel Fitness for a more lengthy description.
The most important thing is to call first. There are a bunch of downtown Toronto gyms that don't do guest passes at all unless a member brings you in.
Good luck and enjoy TO.