What ways do you use to sneak exercise into a particularly busy day?

You can do strength training, flexibility training, yoga 🧘‍♀️, meditation 🧘‍♀️ anything you want. You can also do some walking around and also anything else that you can think of

While I'm at work I'll do calf raises or wall sits if I'm in a spot that I can. If I felt I didn't do enough of my workout during the day I will do more right before I go to bed or I'll try to get up a little earlier the next day to fit in some extra

I try to get it done first thing in the morning right after I've woken up because I know that I'll struggle even more if I choose to do it later.

Well I wake up early in the morning, find even just 15 mins to yoga and admire the sunrise over Rome, drink a lot of water and get some me-time before the start of the day

I don't think that there's any way to sneak exercise at any busy day.
If you don't have time to go at a stadium for run or even outdoor run, then you can do exercise at your home.

First of all I think it's okay to not do any exercise on particular busy days. But if you really want to, or if all your days are particularly busy you can always sneak some quick ones at any time of the day (a few pushups, squats, sun salutations, etc.) It will only take you 10 min, or 5. Working out first thing in the morning is also a good idea if you can make it stick and feel strong enough.