Ensuring the “harsh” taste

Hey guys, I am finally going to start brewing my own booch after being in this subreddit forever and spending hundreeeeds on kombucha over the last few years. It only took me long enough. Lol

I only drink GT Dave’s because I have colitis and it needs to be strong and not like juice. Some of the other ones are just not good. How can I ensure it's strong like this? Is there a certain ingredient that makes it more “harsh”? Should I use a limited amount of fruit/juice? The fermentation time?

Thanks!