Is there a really annoying girl at your school and she's so fake? Well, say this:
Me: Hey, I have a nickname for you.
Her: Really? What?
Me: Sweet-in-low.
Her: Why?
Me: Because you're artificial.
Listen up, buttercup. This joke is all about calling someone "artificial" which means they're fake, like the sweetener "Sweet'N Low." Get it? Because you probably don't.