Coughing non stop

For those of you have had a child who gets poorly and coughs NON stop, I’m talking 9:30pm-3am last night, how do you help them?! She hasn’t napped yet today because she can’t stop coughing & it’s making her gag / sick a bit. I’m at a loss and I know she can’t help it but it’s so frustrating for me too. She’s getting so ratty and annoyed as she is knackered. Help please 😭