Using hot water is your best bet if you are doing a full cleaning. I would not use any kind of household cleaner, especially those with bleach or any harsh chemical. Dawn dish soap should be alright if you rinse, rinse, rinse.
If you are doing small, routine cleanings inside the tank, I recommend either using a dampened paper towel for the walls of the terrarium. Just never use any kind of chemical or cleaner around your beardie, and you should be okay.