I imagine that there’s very little use case for this, but I wanted to highlight it anyway. The small grocery chain Buehler’s (which only has 14 stores – all of which are in Ohio) sells third party gift cards online.
It looks like you earn rewards points on the gift card purchases. I’ve no idea how it codes though; it’s at BuehlersGifts.com which is separate to their website, so perhaps it codes as a grocery purchase.
I’ve no idea why you’d want to order these gift cards from Buehler’s online though, but perhaps someone has some kind of play out there where it might make sense (this isn’t a hint – I have zero idea!).