M.W.
If you are putting anything other than water in them at night I would say stop that and only give them water at night. Maybe leaving the sippy cup on their nightstand or close by the bed then if they wake up in the middle of the night they can easily reach for a drink of water. Or if you want to get then totally off you can try telling them a creative and imaginative story every night about letting their cups go over a few days or weeks to prepare them for completely letting them go.