Does milk exist in D&D?
Not per se, but it's assumed to be included in the Food, Drink, And Lodging category of the Equipment section. Please don't start to argue about stupid things, it's as simple as the DM won't allow something that is combat relevant if it's not on a handbook.
Alternative Potion of Stinking Cloud ??
Y'know ... for Orcs.
You know they can't digest Milk right?
Here lemme explain the joke (pulls out chalkboard and ruler) ...