Jack In The Box and McDonalds are both back with their $1 summer drink promotions. At McDonalds any drink is $1 so why not order the largest size?

At Jack In The Box the largest size is $1.

But I just went through a Jack drive-in where I was told they ran out of large cups, so I had to get a medium. When I looked at the electronic order screen it showed I was being charged the regular price for a medium which was well above $1 for the large.

"What about the $1 special?" I asked.

"OK" the order taker responded, and the price was reduced to $1.

Still... only got a medium drink.

This is the first Jack In The Box that has told me they ran out of "large cups" but I wonder if others might as well?