Can you remove rust from a car?

Depends on the extent of the damage. Body panels can be replaced, but the chassis is whole other story. Both can be fixed if things haven't gone to far.

sand and paint if it is not too bad

No. I don't know how.

Old myth: coke... I don't know if it works or not... just an old myth I've heard about.

you can purchase rust-neutralizing spray paint from home depot or an auto parts store. i’d grind it down with a wire-wheel or sandpaper and spray the rust neutralizer on it, then prime and paint. i just did this to my bumper and ended up discovering that the rust was quite extensive, and i poked a couple of 8-inch diameter holes in my bumper. that’s a whole different fix – realize that that may happen to you as well!

I have had great luck with “Naval Jelly”, made specifically for rust removal. It’s easy to use: brush on, hose off. It’s usually available at hardware stores and is relatively inexpensive.

don’t know much about rust, sorry.

Of course you can, but it’s a lot of work. If you don’t have the tools/know how, just take it to a body shop to get the work done.