I would have accepted the offer. Taking my own personal urine to make the batter, and the feces from a baby to add toppings to the pizza, I would take VIDEOS of my steps, and make it go viral...and laugh after I crossed the border to spend the rest of my days in Thailand..
That sort of thing may really start to catch on. Rather than risk a law suit - give them their cake. Just remember to wash your hands afterwords. You won't want to eat with those hands after you make that cake.