Weaning off milk

Daisy

So my 1 1/2 year old daughter still wakes up at night for milk. We give it to her in a sippy cup, just recently my significant other wants to start weaning off the milk but he wants to water down the milk!! And i don’t think that’s the best idea. Anyways is watering the milk a bad thing???? And is there any tips you guys have that would possibly work?? Thanks!!