If they pull me over for speeding or something and ask if I consent to having my car searched, I'd say, "holy SHIT no, NO, omg no no no no no fuck me no no no no". And then if they fall into my trap I'll tell them it's just pepcid AC and we'll have a big laugh.
Even if they don't frame you by throwing some real fentanyl in the bag, they can still probably get you legit charged with "obstructing an officer" or whatever it's called