Three short moments sit side by side here, and the poem lets us connect them ourselves. The first is about a man's rants, and the speaker hears something underneath the noise: a "rattle of fear." The loud talk seems to be covering anxiety rather than expressing confidence.
Then the focus turns to the speaker. Also "foxed with wine," they relieve themselves against a bridge in the cool of the evening. The title, "Drunks," is plural, which suggests the speaker may be counted among them. That small shift makes the poem less judgmental. The speaker listens to the ranter without looking down on him, and then does something just as undignified.
The mood is quiet and a little wry. The evening air and the bridge give a calm, ordinary setting, while the drink and the fear add something rawer. The poem seems to suggest that these men share more than they'd admit.