Take a look at the sentence again:
Orange juice, toast, and cereal might be a healthy breakfast, but Ricardo
always hits the snooze button on his alarm too many
times all he can grab is a stale pastry
and soda.
The problem occurs between times and all. Ricardo always hits the snooze button on his alarm too many times is a main clause, so it can stand alone as a complete sentence. All he can grab is a stale pastry and soda is the next complete sentence. Because these two parts have only blank space between them, they make a fused sentence, a major error.
To fix the problem, you could put a period after times and then capitalize the A for all.