The plastic exo terra spray bottle has a dreadful chemical smell though I washed it and let it air. I am afraid to use on my birds. Advice?

I would advice you put a tea spoon of natural vinegar in the bottom of the bottle and then fill it with about one third with hot- simmering water. if you boil water in a kettle or pot like i do. Do Not place the bottle in the microwave as it may put the plastic chemicals into the mixture. 'swoosh' it around and let it sit till the water cools. then dump it out, rinse well, let it dry and air outside. And it shouldn't smell like chemicals anymore, and its naturally clean and safe to fill with water and use. I recommend buying distilled water from your local store/walmart carries gallons. but tap should be safe for your bird non the less. -hope you find this method helpful.

I was wondering why I received mine already wet inside like it has been used?

Sounds used to me. Paper instructions should have been inside

use this for a baby bearded dragon?

Yes you can just be careful that you dont blast him with the jet stream. Also you probably dont want to spray him directly at least not until he or she is used to it. My bearded dragon loves it and its sooooo much easier than using a spray bottle. I love it! Hope this helps