how to warm up breastmilk

my son will only drink breastmilk in the bottle if it's really warm. warm like straight from the boob.

what is the best way to achieve this level of warm? the milk will be cold coming from the fridge.

thank you!! I love this group & all the help i get from it. ♡

I want to add that hell be at the babysitters. so I need something practical lol