Don't think this would stop most drug dealers from accepting it, plus the kid could easily go exchange the cash for smaller bills ("Can I please get two tens, three fives, and five ones?) at a bank. What you should probably do it get the kid a WalMart card. Or even better an Amazon card. Amazon has pretty much anything the kid could need, but not weed or alcohol.
Also, if you don't want the kid to spend money on weed or alcohol, and you know that is something the kid is prone too, maybe don't give it in a card that says "Celebrate, you've earned it" because you're really sending mixed messages there.
Also, if you don't want the kid to spend money on weed or alcohol, and you know that is something the kid is prone too, maybe don't give it in a card that says "Celebrate, you've earned it" because you're really sending mixed messages there.