You can go down the Horlicks / cocoa route; there's mileage in that. If you check out any large supermarket's range you'll be able to sample a different flavour every day for a month. Salted caramel and buttered popcorn are currently selling well. The problem is that after a few days you'll be snuggled up on the sofa of an evening, in a onesie, watching re-runs of The Gilmore Girls on Netflix.
Another thought is to recreate alcoholic drinks as close as you can without actually putting alcohol in them. There's alcohol free beer of course but somehow this seems like cheating. Or what about Virgin cocktails? Although I can see that leading to the sofa / onesie / Netflix box set situation.
I often just drink tonic on its own. I mean, it's not nice but at least you can kid yourself that there's gin in it. Or add an elderflower cordial. Or chew hops. Or something.
Anyway, good luck for the month.