OK sounds like a scam, but there are lots of things you can do in a few minutes that makes a lie of "I have NO time to exercise". No props, weights etc needed. Just a space big enough to let you do what you do. (Also called Ghetto workouts or prison cell workouts). If you know 'em, lets hear 'em.
I'll start …
Pushups-to-exhaustion, three sets before noon. (Inspired by a YouTube video).
I used to have the goal of doing 100 pushups a day, didn't matter if it took me 10 sets of 10 or 100 at a time. I'd work my way up and figure it out. Eventually, I'd bang out about 3 equal 30-35 pushup sets a day every day.
Once I was comfortable with that, I'd try to do as many pushups in a row as I could. Once that peaked, I started to see how many I could do in 60 seconds. Now I'm up to about 75 in 60 seconds.
Now I'm doing 75 pushups over 1 minute 3 times each morning with rest in between. So I take a minute after I wake up to do the first set, usually the second set before I leave for work, and then the third set in a minute before I eat my lunch.
So that's 225 pushups in 3 minutes and feeling great before lunch.
I like pushups a lot … I think they are very underrated as an exercise (biceps, triceps, lats, trapaezius, deltoids). If you do enough of them, you start to feel it in your core because you are actually doing a plank. I also think they are a highly functional bodyweight exercise. You can also vary the position, location and placement of your hands if you get bored.