I work from home, so did explore co-working spaces when I first moved to the city. Some do have a day pass option, some require membership to work in their space (CSI comes to mind). Tract 9, in the west end, offers a 1 week free trial, which is worth checking out. Haven (formerly RandomWork) also offer days, and were the most competitively priced relative to other spaces. If you're in the west, I'd also recommend the Theatre Centre's cafe. It's attached to an incubator, so has great internet and a good co-working vibe relative to other cafes in the area.