Like mentioned above, if your commute is not too long, just take it easy and go in your regular street clothes just as if you were to walk to school. You will not sweat if you don't make it a workout. Riding a bike in regular clothes can easily be done. It's only when you have some distance involved like up to 10 miles with hills etc. and you have to keep a regular pace to get somewhere on time, then you have to get specialized cycling clothes to be comfortable.