Re-invest it in your business. Hire someone to help with SEO and SEM. Hire someone to write content like a blog. Find someone to manage your social media, moderate a discord and build community around your product. Spend (more) money on ads
You aren't going to find a better investment. A well performing mutual fund might get you 10% a year. Something riskier could get you up to 15%. I'm willing to bet you can make much more than that just by re-investing in the asset you already have. You can also avoid paying taxes on that money in the short term.
If you don't want to do any of that, just leave it in your business account until you do.
1. If it's something you think is inherently short term (say it's about NFTs and you don't think they'll last) take a portion of the excess income and invest it elsewhere, even if its from the same corporate entity you'll be able to shift to multiple revenue streams.
2. Sometimes with these smaller opportunities it's more fun to just hyper-focus on making the most delightful experience possible, instead of squeezing out another 40% by optimizing SEO and user funnels. I know a couple people that ultimately built much larger companies because they started in something that was a labor of love before the market really even existed (e.g., a podcast app) so when the sea of people finally came they had the most polished offering. You said you didn't really want to focus on growing the company, so this is a happy middle way you could think about.
You aren't going to find a better investment. A well performing mutual fund might get you 10% a year. Something riskier could get you up to 15%. I'm willing to bet you can make much more than that just by re-investing in the asset you already have. You can also avoid paying taxes on that money in the short term.
If you don't want to do any of that, just leave it in your business account until you do.