What did Yahweh tell Ezekiel to eat and drink while he lay on his side?

Yahweh told Ezekiel to eat barley cakes and to drink water [4:9; 4:11; 4:12]

Why did Yahweh tell Ezekiel to bake using human excrement within the sight of the house of Israel?

Ezekiel was to bake using human excrement as a sign that the food the people of Israel would eat among the nations would be unclean [4:12; 4:13]