D.P.
I dreaded this.
I let it go for way to long and it will get harder.
He had O. bottle with his snack before bed.
IF you warm the milk now, warm it for the sippy.
I have to say though, when my son had his before-bed-snack and I handed him a sippy cup to go with it--he NEVER flinched! Nada. Nothing.
I think it was harder on ME than him to ditch the bottle!
Just pick a day, put ALL bottles away & do the switcheroo.