Most singers are aware how much what they drink and eat can affect their general health and especially their voice – and even more so just before a performance. This also varies hugely from one performer to another. I knew a brilliant tenor who would down a hamburger with the works and a thick shake before every performance. I don’t know many people who would, or could, do that and have a great performance. But it worked for him. Most eat lightly before a performance so that whatever they’ve eaten has finished digesting by the time they’re on stage.