I've found a caterpillar

Hi,
There was a violent windstorm and this light brown caterpillar who is a little over an inch long and about as thick as a pencil was laying on concrete. I thought s/he was knocked unconscious. S/he is moving, however, slowly around in the glass vase I washed out for it. I filled it with shallow water then sliced a green apple up and laid the pieces on the water and placed him/her on them. Ever since I found it there has been clear green bubble(s) forming out his back end. Is that poop or what?
Am I taking care of it correctly, should I put a leaved twig in the vase with it as well?

Take it out of the vase and put it on a tree limb, or even better, amongst some leaves on the tree which it will feed off of. It will make itself a new home until it finally becomes a butterfly. Let nature do it's thing, it doesn't need your help.

Caterpillars don't need to be fed, all the nourishment they require is contained within the cocoon as well as leaves on trees that it eats.

Here are some links you might find useful and educational:
http://www.backyardnature.net/caterpil.h…
http://www.discoverlife.org/mp/20q?guide…
http://www.uiweb.uidaho.edu/so-id/entomo…

I would definitely put in some plants so that it isn't sitting and possibly drowning in the water. You might also want to try to identify the caterpillar in order to take better care of its needs. Or even put it outside it will likely find it's own food shelter and or nature will take its course.

Put it in a tree or a plant in your house if you want to keep an eye on it

Give it to me

LOL