By definition, it’s no surprise when someone orders their usual, but what’s the joke?
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He ordered a bottle of pop, as in “pop goes the weasel.”
Jack and Coke is a standard drink (Jack Daniels…whiskey, I think).
The joke is that a Jack in the box, famously known for surprising people does something that is no surprise, this failing his purpose. Hence the derisive comment.
All three of those are plausible and it’s plausible the artist actually intended all three.
What Philip said
I like the “Jack & Coke.” I didn’t think of that one.
Comics I Don't Understand 
He ordered a bottle of pop, as in “pop goes the weasel.”
Jack and Coke is a standard drink (Jack Daniels…whiskey, I think).
The joke is that a Jack in the box, famously known for surprising people does something that is no surprise, this failing his purpose. Hence the derisive comment.
All three of those are plausible and it’s plausible the artist actually intended all three.
What Philip said
I like the “Jack & Coke.” I didn’t think of that one.