Uh, lightbrite, fruits and vegetables don’t need kashering.
The only kashrus issues would be bug infestation, since bugs are assur to eat. Each veggie/fruit has its own ways of dealing with bug-removal, which can include soaking in soapy water. There are some that are so difficult to check and remove bugs that we are told to avoid them altogether.
The other issue, which is not a kashrus issue per se, applies only to fruits/veggies grown in Eretz yisroel, and that is that they can’t be eaten until terumos/maasros are taken off (tithing) and fruit can’t be eaten first 4 years from when tree is planted (orla and neta revai).