University of Waterloo

Yes, of course, you can apply for Canadian universities. And yes, you can also appear for SAT exam.
SAT Eligibility 2018: Key Features
Although the College Board does not prescribe any particularSAT 2018eligibility criteria, students aged between 17-18 years of age mostly appear for the SAT 2018 test to get admission into colleges for undergraduate studies. Ideally, high school students opt for the SAT examination. Age Limit- SAT eligibility 2018 do not state any age limitation to appear for the SAT test. If a candidate is 12 years old or younger, he/she can register for SAT by mail ONLY. If a candidate is 13 years or older, can create the free College Board account to register for SAT 2018. According to the SAT 2018 eligibility, if a candidate is 21 years or older, then he/she must produce an official government-issued photo ID, like a drivers license or passport, to the test centre. Hope this helps you. Be free to share any problem you have. GOOD LUCK.