Cat poo smells like vinegar, excessive drooling, diarrhoea

My 4 year old cat has recently started to vomit, drool excessively and is now starting to have diarrhoea that smells like vinegar/sour. He is eating less then he usually does. Is he sick?

Yes, and he needs to be seen by a vet ASAP. Please keep us updated.

my parents are away for a week, what can I do until then? I am really worried about him

You cannot wait for your parents to get home.

It could be he ate something toxic, and he needs his system flushed.  Only a vet can help with this.  You need to find an emergency vet and contact your parents for some way to pay if you are unable to manage it yourself.

I left my cat alone for a while and he started to get better. Since then he has been fine, only vomiting once every 5 days or so. There has been a lot of improvement.