<em>Saque la basura </em>is a formal command in the imperativce mood in which the verb<em> saque </em>agrees with the ommited subject pronoun <em>usted.</em>
Saque la basura is an imperative which means that is a formal command. We use the imperatives to give instructions and orders and we do not have to use a subject pronoun to start the sentence. The right structure is Verb in the simple present + complement.