The Cheap option is that for summers remove leather stuff from your car especially seat covers. use shades and put some shade on the front screen too. park your car under some tree or some place where there is not direct sun light.
Reasons for corolla not being that hot.
maybe it was parked under sun for less period of time then your car.
maybe your friend has some Uv protection film on the windows.
another thing is that corolla's ac is better then caltus which will result in cooling the car faster then caltus and do to that you felt it was not as hot as your car.
I have a corolla and it does get nasty hot when parked under the sun for some time.
so what i do is apply shades and take off the passenger side shade and put it on the dash to keep the steering covered.
too cool your call quickly open the windows for 2 min or more and keep the ac on.
