Gwen found the option to change what breasts lactated, and saw in addition to many, many preset options, there was also a text box where she could input anything she wanted. Anything... Oh, the possibilities.
There was no need for her lactation to be a beverage, or even edible or safe at all. She could lactate lotion, or acid (and found that if she lactated the latter, the Breastinator would also make her body immune to it). Hell, what she lactated didn't even need to be a liquid: dildos, kittens, and bottles of perfume were all viable options.
And why limit herself to things that already existed? Detached copies of her own head that she could still control... Pills that instantly changed the consumer's genitals to the opposite sex... Milk that made anyone who drank it obey any command she gave for a short time...
No, having a text field could do more than that. What if she typed in an abstract concept? Could she lactate apathy? Jogging? "Being a goth"? What would those even look like? She had to experiment...