If a host offers you a drink and you are the guest, you leave a little drink at bottom of the glass as etiquette. Is this considered wasting food ? Is it a sin ?
Wasting itself is haram even if its a little bit or not, its because there is people that cant afford to buy or got the same luck as us (Alhamdulillah) to have Food, water and many other things. I'm sorry if I said something wrong but this is what I think about this subject. This is how we do it in our family we dont waste food at all
I can't say I've ever come across this as etiquette. What's your source?
Generally, the idea of a party is to be social and gregarious and not to eat and drink all at once. Hence drinking slowly is etiquette and this is why it's likely that at the end of a party food and drink is left as everyone is following this rule of decorum apart from the odd guest who doesn't know how to behave.
It is haram to waste food and drink, though. And one would expect the host to donate the food and drink to a charity ...