Same thing. It has to be things they would normally chew in the wild. Rabbit safe branches like willow, apple, bramble, birch, etc. And yes, they do destroy them in no time. Which is why it's preferable if you can find a source in your yard or area that is free for you to gather yourself, and is uncontaminated with pesticides/herbicides and not next to road pollution.
If you don't have this kind of access to natural products, one thing that can be used is timothy or other grass hay cubes. They aren't a replacement for loose hay, as rabbits don't really consume a large portion of them, but they can chew on them as an activity. So maybe try that. Stick with the grass hay ones like timothy, and not the alfalfa, and make sure there are no other additives, just plain chopped hay. There are a few different options available on amazon or online, or you may be able to find grass hay cubes at a farm supply.