Idea! They could offer a look-see for guests ONLY IF THEY HAVE A LIBRARY CARD! That's right, you don't have to have an ADR to see the inside of BOG, but you must have a card if you (wait for it) WANT TO CHECK IT OUT!
You need a reservation to enter, but you can tour all the rooms inside without eating. Just get a breakfast reservation and then just order a coffee or fountain drink.