Jun 29, This recipe for homemade watermelon vodka slushies are meant for adults! This recipe for frozen cocktails uses watermelon vodka blended. Aug 12, Boozy. Watermelon. Slushie. We just strung together what are arguably the three greatest words in the English language and turned it into one. Watermelon puree is frozen, then blended with vodka, melon liqueur, lemon juice and simple syrup.