Milk with that cookie for me, a tall glass and cold. Some may denigrate milk as childish, but nothing goes down with cookies so well.
And I hope those cookies have chocolate chips.
Argument?
My husband likes beer with his cookies. His mother (who is German!) is horrified by this.
I like coffee with most cookies. A tannic red wine or port is nice with the dark chocolate varieties.
I love me a cup of tea, but with cookies, milk is even better.
Hot cocoa, of course, is the gold standard.
it depends on the cookie. Chocolate cookies, brownies , etc., require milk. If there’s no milk, put the cookie down until you get some. Oatmeal cookies are good with Coke. Peanut butter cookies need chocolate milk.
StG
Coffee, always. I haven’t had a glass of milk since I was a kid.
Coffee is my preferred cookie accompaniment. The bitterness of the coffee balances the sweetness of the cookie.
Milk, and, I, too hope they are chocolate chip.
I believe the saying goes something like this:
True, humans are the only species that drink milk after being weaned, but then again, humans are the only species that developed chocolate chip cookies.
Milk, maybe tea if its one of those not so sweet European/UK cookies, like Bischoff.
StGermain has it, it depends on the cookie. Anything with chocolate requires milk or better yet, hot chocolate, prime examples are Pepperidge Farm Milanos or anything chocolate-filled and elf-shaped. Coffee with cream is pretty much all-purpose and can go with anything, especially biscotti if they qualify as a cookie. For basic non-chocolate ones like shortbread or Sandies, then tea is my bevvie of choice.
It’s like wine, you have to pair the drink to the meal. 
Coffee, for that satisfying hit of bitter-sweet.
Ach, I’m livin’ among the heathens! Milk is the only thing to go with a cookie. And if you have a cookie that doesn’t go well with milk, then you have a lousy cookie. This is simple stuff,folks. I shouldn’t have to be teachin’ you this at your age.
tea
milk if ok if you are not old enough to drink tea 
My favorite accompaniment for a cookie is another cookie.
Coffee. Cookies are just too sweet with milk.
Milk. “Milk and cookies” – it even sounds right. Let’s see, “tea and crumpets”. (Although I’ve never had a crumpet.) And “coffee and coffeecake”.
All good choices. Cocoa too. But there is a reason you leave cookies and milk for Santa. (That reason is when Daddy drinks it, the caffeine might keep him awake).
Coffee and cookies are a nice snack.
I like milk. I rarely have it with cookies. Not sure why. I just don’t think about it.
Coffee is my choice, but milk will do. They’re bitter to neutral. Tea is fine, too. But cocoa? Way too much sweet for me.
What you need is a Nice cup of tea and a sit down.
Sadly the site has been dormant, or possibly diabetic coma, for nearly a decade.