纯牛奶越喝越纯蒙牛奶越喝越梦
[chún niú năi yuè hē yuè chún mĕng niú năi yuè hē yuè mèng]
Drinking pure milk makes it purer; drinking Mongolian brand 'Mengniu' milk leads more to dreams. It's a pun on the name of the dairy product brand Mengniu. The first sentence implies growing simpler or purer, while the latter refers to indulging oneself into dreams or fantasies.