Hello Uday,

Yess, you can wear jeans and sweater in JEE mains 2020.

But make sure that it doesn't not have too many pockets and try to wear comfortable loose clothes and simple trousers or jeans.

Don’t wear any fancy scarfs, stoles, caps, goggles, wrist watch etc.

Don’t wear jewellery items like rings, earrings, bangles, bracelets, anklets etc.

Good luck,

Hope it helps :)