plain water?

where I grow my plants it's really hot and I was wondering if I spray the plant with just water and when the sun hits the plant will the leaves get burnt?

It is possible that it can get burnt. The only problem with spraying the leaves when the sun is out is that when you do spray it makes little droplets on the leaves that act like a magnifying glass and will focus the light on one part of the leave burning it. best time for spraying your pants would be at night.
Im guessing that you are growing outside? If so i am guessing there isnt to much that can be done but def spraying the leaves while the sun is out is not the answer.