What should I do with $40k cash besides letting it sit in my checking account?

I invest pretty heavily into retirement accounts, 401k and Roth IRA.

I don't really have any bad debt.

Car loan @ 2.9% interest, mortgage at 5.8% interest. That's all my debt. Nothing I really need to consolidate or pay off.

I've got an emergency fund.

I'm planning on using the cash as a down payment on a second piece of real estate. Either a vacation home that will be a short term rental, duplex in my city I can manage myself, or commercial real estate of some sorts. Idk yet, I haven't made up my mind.

But right now I've got about $40k in cash just sitting in my checking account.

The issue is when I'm trying to make a play to invest further in real estate, I'd need my cash to be fairly liquid if/when the right deal comes up.

Im honestly trying to save up about $80-100k cash to use for a down payment, so I'm not there yet. I'll likely need another year and change to get there.

What else should I be doing with this $40k cash than just keeping it in my checking account doing nothing?