Before my best friend ran the New York City Marathon for the first time, she asked me to bring exactly one item when I spectated from the sidelines: not a sign, not a snack, but a large cup of ice water from Dunkin’.

I wasn’t surprised. It was the same drink that fueled many of the training runs I’d joined her on over the summer. Besides each other, the only thing that got us through the long distances under the summer sun was the thought of the 32 ounces of pure bliss waiting for us on the other side.

You might be wondering, “It’s water; what could possibly be so special about it?” Although you’ll have to experience it for yourself, I find that there’s just something about the combination of the plastic Dunkin’ cup, the straw, and, of course, the ice that makes the chain’s water seem extra refreshing.

People often rave about pebble ice, but I remain steadfast in my belief that Dunkin’s ice — perfectly smooth, not-too-large cubes — is the best in the fast food biz. Even better, you can snag a large cup of this icy perfection and water for $1 and some change.

In the words of my marathon-running best friend, Olivia Spofford, “Dunkin’ ice water is an experience. It’s like how when someone else makes you a sandwich, it’s always so much better than when you make it for yourself. When someone — specifically a Dunkin’ employee — makes you ice and tap water packaged in your favorite coffee cup, it feels extra nourishing.”

I can attest that this simple beverage satisfies thirst infinitely better than bottled water ever could. When I spot bottles of Poland Spring in the fridge at a deli or convenience store, I can’t help but think, “Why bother? It can’t even compare.”

There is one catch: This isn’t a drink you can find on the Dunkin’ app. You must order your ice water in person at a Dunkin’ counter. You won’t see it listed on the menu either, and it’s an “if you know, you know” situation. Prices vary a bit by location, but a large ice water will usually cost around $1.09 with tax. It’s worth every penny.

Customers often joke online that you’ll never get the same drink from Dunkin’ twice, because your coffee of choice seems to always come out just a little bit different compared to the last time you had it — sometimes it’s incredible, and other times not so much.

You know what drink doesn’t have that issue? The ice water. It’s always refreshing, and it’s the exact same every time you order it. (The rare exception to this is the one time Dunkin’ served the water to me in a paper cup instead of the usual plastic option, but I can assure you that was an anomaly.)

Next time you’re craving some hydration while out and about, skip the bottled water and head to Dunkin’ instead. I promise your thirst will be quenched effectively than it ever has been before.