5x $20 lottery tickets. Most lottery tickets have a 1:3 - 1:5 win rate, so if you're lucky enough he might win literally nothing. Nothing else on this list gives the friend hope. Hope unfulfilled is the definition of cruelty.
I'd go one further. Scratch off the verification code of each of the lottery tickets scan it. And remove any winning tickets. You don't have to hide this. We're trying to give a crappy gift so if they look and see that you've already scratched them. Your gift then becomes here's $100 of losing lottery tickets. It's beautiful
This is dumb because even if there are winners in the pile, now you can't even cash them in yourself because the codes been scratched. So the joke will be on you when it turns out one was actually worth a million
He was going to spend $100 on a gift without getting anything in return in the first place, whether the gift was lotto tickets or 1000 pairs of used socks. Also, many (most?) states don't have prohibitions on revealing the validation code, and unless you have some information not presented in this post, you don't know what state OP is in.