Not to be rude, but if
If you gave me any FizzBuzz-like question, I would expect to fail it.
Then you can't code at all. The only thing fizbuzz do is weed out candidates who cannot code.
If you want
reasonably respected coding qualification
The only thing you can do is get mileage. And lots of it. Implement small webapps, small prototypes, write toy games, perform data analysis of some public dataset, even competitive programming would help.