Four short lines, and a lot of mood packed into them. The speaker praises sand as "good and simple," then adds a odd claim: it's "the only thing like a thing." Sand, in other words, feels solid and honest, a plain object that is just what it is. That praise carries a hint of contrast, since the poem then points to something messier: "the wine bar oysters" that "brought me to bed."
The title puns on "sand bar" and "wine bar," linking the beach to the night out. Judging by the lines, the speaker seems to be nursing a rough evening, perhaps overindulgence or a bad oyster, and longing for something uncomplicated. "Brought me to bed" can be read as sick or simply worn out, and the poem leaves that open. The tone is dry, wry, and a little rueful. It's a small joke with a real wish underneath: to be done with fancy things and rest among plain ones.