Waking night only blue milk

Im a first time mum and a bit confused I don’t have much help 😫my little boy (12months) had about 3 bottles everynigjtnfornas long as I can remember and all the shops have closed and I ran out of his formula so, I decided for the night I will give him the full fat milk he drinks in the day time , but how do I keep it nice for him so it’s not freezing cold out of the fridge, Shirley if I leave it out it will go bad 😬sorry if this is ridiculous but I’m just so confused