The moody foodie came into Bob's Burgers dressed as an Orthodox Jew and ordered a cheeseburger. Cheeseburgers aren't kosher based on a command in Exodus (repeated in Deuteronomy) to "not boil a young goat in its mother's milk." Tradition uses this to prohibit cooking, eating, and/or benefiting from a combination of meat and dairy products. Hence the Orthodox Jewish costume gag.
Burger of the Day: If Looks Could Kale
Burger of the day: Little Swiss Bunshine Burger (comes on a buttered bun)
Final burger - "The Final Krautdown (comes with sauerkraut)"
Store next door - "Grindecologist Coffee Shop"