Make me a sandwich, bitch,” is a semi-literal phrase used less as a command and more as a denigration, for obvious reasons. I came across a screenshot of someone on Twitter tweeting it, so I did some searches on the phrase, both with and without the comma. Nearly all usages I’ve seen online do no include the comma, which I partially expected. The people using this phrase aren’t likely ones to be concerned about the grammatical implications of not using a comma, especially in this case.
If you’re asking someone to “make me a sandwich bitch,” you’re asking them to create—or, less literally, “find”—someone (maybe a female, but really just a being of any sex employed in a subservient role), who has “making sandwiches” as a primary directive. To better understand, the phrase, “Yeah, she’s my sandwich bitch. I don’t loan her out.” has the same usage of this accidental “sandwich bitch” designation.
This term, if you think about it, is a lot more useful for those of us with long time preferences than asking the bitch in question to make a sandwich as a one-off mission, as is the implied case when using the comma. Now we just have to wait for technology to catch up with our demand for dedicated sandwich bitches.