Adam Clarke on 1 Samuel 10:3

Three men going up to God to Bethel - Jacob's altar was probably there still, Gen 28:19. However this might be, it was still considered, as its name implies, the house of God; and to it they were now going, to offer sacrifice.

The three kids were for sacrifice; the three loaves of bread to be offered probably as a thank-offering; and the bottle or skin full of wine, for a libation. When the blood was poured out before the Lord, then they feasted on the flesh and on the bread; and probably had a sufficiency of the wine left for their own drinking.