I've been thinking there should be a 'second' (?) currency. Basic income would be paid in this currency and you can buy certain stuff with it. Food, rent, gas etc.

Then we keep our current currencies right next to it. You can buy the same stuff but also other 'luxury goods' (or find a better nicer name for it)

I know that the Dutch government already makes this distingsion where we have 6% tax on food, art, medicine (and other stuff) and 21% tax on the rest. Since the distingsions is there and recognized, we can utilize it for other purpuses.