What’s Your Go-To Budget-Friendly Fitness Trick?

I’ve been digging into ways to stay fit without draining the wallet, and I’m curious what’s worked for others. Walking or running outside costs nothing, and bodyweight exercises like push-ups or squats don’t require a gym membership. But I’d love to hear other ideas especially ones that might have a bigger payoff over time, like investing in a single kettlebell or using resistance bands. Anyone have a favorite frugal fitness move that’s kept them in shape without breaking the bank? Bonus points if it’s something you can do at home!