Crack.
I think that is the secret ingredient in their strawberry milkshakes.
To tell the truth, I don't eat fast food much. But for some reason, these milkshakes make me feel like a junkie. I'm like "Milkshake, milkshake, must have, now!" and so I rush to get one (large, always). As soon as I start drinking it, I know that the taste is really unnatural but I KEEP DRINKING ANYWAYS.
And then the cycle repeats. Seriously, what are in these things!?