You can drink your breast milk by expressing it with a breast pump or just squirting it into a cup. Some women use breast shells to protect clothing, and it is possible to drink the leaked milk from that.
Apparently it takes a bit like goats milk but isn't too bad in a cup of tea or coffee. It has an almond milk taste, like milk with sugar in it and no aftertaste as there can be with some animal milk.
Some women use it in cooking as it is low in fat so better, health wise, than cow's milk.
Models drink it as they believe it has youthful properties so that's as good a reason as any I can think of!
There is no proof that it has benefits in that way, but it can give you an energy boost, and it's free :-)