Being a student, I will assume OP means near Bay and Yonge stations. Correct me if I'm wrong.
You could hit up the ROM, a short walk west of Bay station.
You could get a book from the reference library and hang out at Balzac's coffee.
You could simply walk along Yorkville avenue, get some sun on the big rock while you watch the rich, tight bodies walking up and down the street. Also a nice place for coffee.
For affordable food, try M'Zaar, or Xtreme taste, or the food court under Hudsons Bay at Bloor/Yonge.