"I cannot find the orange juice."
Translation:Ich finde den Orangensaft nicht.
Definitely no comma in this sentence. Usually, "nicht" is placed after the accusative object, i.e. here after "den Orangensaft". http://www.canoo.net/services/OnlineGrammar/Satz/Negation/Stellung/nichtkontrast.html?lang=en
On a plus note, I read a couple comments on a separate conversation which ended in me learning that when a modal verb is used (soll, kann, etc), the main verb goes at the end of the sentence. Therefore the nicht would be prior to negating the verb (if that's what you're negating)