Let me simplify this one for you. See, we can sit and thereby be sitting. We can also do something while we are sitting. Like read a book while we are sitting. But there are some things we simply cannot do, like sitting ‘for or to’ do something.
Initially, I thought it was only a few people, who say something like this. Over time, I have heard it from numerous people cutting across states and regions. And then recently, a friend of mine was over for lunch, and after chatting for a bit exclaimed, “Can we sit for lunch? I am hungry.”
You can guess where that came from. Absolutely! It’s the influence of Indian languages on the way we construct our English sentences. In this case, this is a cool rip off of ‘खाना खाने बैठे?’
What works here are some really simple and grammatically correct options such as ‘Let’s eat! I am hungry!’ or ‘Can we eat, please? I am hungry!’
So remember, you can be sitting while you are eating, but you can’t really sit to eat 🙂