Just for share of experience, baby in between 7-8 or 9 months may refuse (or don't like) to drink milk because
a) they have tasted adult food and found it more delicious
b) they may have teething problem so they don't drink milk
Situation may turns better after 1 or 2 weeks time. For me, I give him little milk but more frequent, i.e. 3 hours for 150-180 ml each time. Just as much as he can, then let him go if he really doesn't like.
What about if we need to travel, how can baby eat congee? BB is now 12 months but only has 3 teeth, if I planning to take him travel, how to take care his meal?
I agree with EOR. You can try to give your baby 3 times milk a day since the main nutrition for a baby is come from milk for his first year. Do not give your baby too much snack/juice or congee supplement if he has poor appetite for milk. For better nutrition, you may give your baby cereal with formula rather than congee. Some people say 開奶茶 may work and you may try this.
One more suggestion for you. If your baby regain his appetite for milk, you can add supplement to your baby just or one hour after taken milk. That will not affect his appetite for next milk feeding. Let your son decide how much he take but not force him to eat. Only he know how much he can eat. This can help him to develop a larger capacity for food. As his body grow up, he will show you his increased appetite for food. Let your son to develop his eating pattern gradually. My son only take few spoons of cereal and five times of breastmilk in his seven months. Gradually, he can eat 4oz cereal(ie.one bowl) for two times and four times BF in his 8.5 months.