Whats a good idea for a logo for this product?

Ok well for english we need to make up our product with a motto, a logo, and name. I've got the name and motto but i can't think of a good logo. My product is a truth potion. It is called Deception Free Tonic (i know its not that good of a name any other ideas please?) and the motto is "Three drops to the bottom line." If you could just describe what the logo could have that would be great. Thanks in advance.