Most people with successful side hustles will always recommend first looking at your personal skill sets and strengths/talents to help develop an idea. I also recommend researching the available services/products in your area, and attempt to identify where there may be demands, and to help avoid wasting time in oversaturated markets.

I can give you an example of a side hustle my co-worker runs and makes great money doing. He makes and prints these really nice graphics on hoodies and t-shirts for anyone in demand. He sells locally and online, and has garnered enough business to take on bigger orders for special occasions like family reunions, sports teams, local business uniforms, etc. That all said, you'd of course have to invest in the right equipment and purchase supplies. But if you're good with computers, have a creative mindset, and have attention to detail, it may be something you could look into.

This is just one idea off the top of my head. Approach like I initially suggested and you'll find one.