Breakdown of Han var så fuld at han faldt på gaden.
være
to be
han
he
på
on / at / in (a language) / of (after nouns like end or start)
at
that
Questions & Answers about Han var så fuld at han faldt på gaden.
Doesn't fuld usually mean "full"?
It can, but when describing a person's state, fuld almost always means "drunk". If you want to say that you are full after eating a large meal, you have to use the word mæt. You would still use fuld to describe a full glass or a full box.
Why do we use på instead of i for "in the street"?
Danish typically uses på for surfaces and open public spaces. You are considered to be physically "on" the street, so it is på gaden. This also applies to similar places, like på torvet (in the square).
Is it a mistake that there is no comma before at?
No, it is correct. According to modern Danish comma rules, placing a comma before a subordinate clause starting with at is optional. Writing så fuld, at would also be perfectly fine, and many Danes still prefer to write it that way.
How would the word order change if I added ikke (not) to the second half?
The word ikke would go right after the subject: at han ikke faldt på gaden. This happens because the second half of the sentence is a subordinate clause, and in subordinate clauses, central adverbs like ikke must always come before the verb.