Your second sentence is not grammatical. The verb reach (to extend, to stretch, to deliver, etc) is (mono-)transitive, meaning it takes a direct object, which in your example would be "you".
The first sentence is correct, but not passive. Don't confuse active with volitional. Plenty of verbs are used with the active voice that don't imply the subject is doing the action of its own will.
The faucet leaked
The window broke
The cake baked
A passive sentence is one where the verb acts upon the subject. The bread isn't reached (the bread isn't in a fixed location and people are stretching out to get it), but you are reached (the bread is moving towards you).
The correct passive would be:
If you haven't been reached by the bread, raise your hands
But this is clunky and unlikely to be said. Instead something like:
If you haven't received the bread, raise your hands
might be said.