If there are berrys, leaves or any dirt, I would leave it. I would wash it before you give it to him/her but don't let him/her eat it just in case: I'm not an expert but if your still not comfortable just don't give it to him/her. I'm not that educated on sycamore tree.
My bun loves branches from the front yard but I wash them before I give them to him. No harm done!
I also give my Shooter twigs. Well i don't "give"
He helps himself by chewing the bushes!
I hope I helped