You can add milk to coffee. Coffee contains fat, protein, sugar, minerals and caffeine and other ingredients, milk is also rich in protein, fat and minerals, etc., coffee and milk ingredients, and will not interact, and coffee with milk can improve the taste of coffee, making the mouth more smooth. Coffee contains caffeine, which can stimulate the nerves and lead to nervous excitement, making it difficult to sleep at night. While milk can generally help with sleep, it does not counteract the stimulating effects of caffeine, so it is best not to drink coffee after dinner to prevent the effects on sleep. Coffee can be taken with milk, but coffee should not be consumed for long periods of time, milk can. In addition, coffee is not recommended for pregnant and nursing women.