That is a weird, but good, question. I always liked VtM's answer to those bio functions: vamps have willful control of their blood such that they can move it around to simulate salivation, perspiration, urination, or what have you. They can also use their magic to temporarily simulate the appearance of life at a cost. If we use that standard, then Sohii could feed you either her simulacrum milk or her bloody essence from her pettanko bosom.
But, you know, one universe's canon is another universe's joke.