The victim was in the Zee Bar in Queen Street, Maidenhead in the early hours of Sunday when he was attacked about 02:25 BST, sustaining neck injuries.
A 25-year-old man from High Wycombe has been arrested on suspicion of attempted murder and released on police bail until 15 December.
Thames Valley Police are appealing for witnesses to the incident.
A shoelace was used in an attempt to strangle a man from behind in a Berkshire bar, police said.