Dunno, I think that's just how the drink is made in some places. Anyway, they're black tapioca pearls... [He trails off, tapping something into his phone.] Looks like this when you've added them in.

[When Izuku flips his phone toward Todoroki, there's an image of said drink pulled up on the screen.]

You'll have a chance to try it the next time we stop by here. [Izuku happily takes a gulp of his drink, keeping his eyes on Todoroki as discreetly as he can. Unfortunately for him, that means he's still pretty obvious about it.]