Would it really be that hard to drill a small hole in the bottom of a liquor bottle, drain the liquor out, fill the bottle with water (with or without food coloring, as needed), then seal the hole with something clear? That way, the seal would still be intact at the top of the bottle.
However, I'm stumped on how he does some of his tricks - whole eggs, cinnamon, glue, etc. I guess if you spent some time on it, you could make some icing that had the same consistency as glue. The eggs are a real mystery, though.