Suzuki calls for spark plug replacement at 7,500 miles. I ordered the OEM plugs and got to work. It's not a difficult job, but there are a few things you need to be aware of before pulling those coils.
Spark Plugs 2015 Suzuki GSX-S750: NGK Spark Plugs CR9EIA-9; Spark Plugs #6289 (4 Pack)
https://amzn.to/3f0hz10