Here is one example.
People could even include a note that says "This is NOT a dangerous substance" so they wouldn't alarm anyone. Another possibility for the note is to say "I thought you would like some sugar to go with your tea."
Here is a quote for you:
The mystery of government is not how Washington works but how to make it stop.
P. J. O'Rourke
Now I think I'll go home and hide my dog.