The Messenger of Allah (ﷺ) said, "if anyone drinks milk, he will say:

اَللَّهُمَّ بَارِكْ لَنَا فِيهِ وَزِدْنَا مِنْهُ

Allaahumma baarik lanaa feehi wa zidnaa minhu

O Allah, bless us in it and give us more of it.

Reference: Hasan. Ibn Majah: 3322