To clarify:

They can only be faked as a receiver, and only if you "customize" your receiving zap node. Or if you write some scripts.

For sending, you cannot fake it.

Also, if you're not custom-modifying your receiving zap node, then they're real. All the zaps you receive will be backed by sats.

The reason I point it out though, is because zaps distract from normal LN tips. Which cannot be faked.