What was in the bundle of sticks in the Blair Witch Project?

You mean the "package" Heather finds outside the tent, after Josh has disappeared? And she lies to Mike and doesn't tell him about it?

That is supposed to be Josh's tongue and teeth (some say his eyeballs and nose too, but it's difficult to tell), which were (presumably) ripped out, and then wrapped up with sticks and strips of his flannel shirt.

This part of the story bears a resemblance to the Washington Irving story, "The Devil and Tom Walker." In the story, Tom's wife goes searching for Satan in the woods near their home. She never comes back. When Tom goes searching for her, he finds her heart and liver wrapped up in her apron.