xj6 water in gas tank

My son left my gas tank of my 91 xj6 and it rained all night
I've since took out the gas tank to try to drain all the water and gasout of it.
there is a little bit of rust inside and I can't seem to get all the water out
I'm open to suggestions
is there any additives i can put in the tank to help with the rust and
get rid of the water residue inside the tank
please respond
appreciate it

Yes, there is. It is called a gas improver and water remover, I forget who makes it though. Also if you cant find that I would use gas line antifreeze to remove the water.(Gas won't freeze)