Pick your lift. Select a weight around 60% of 1RM. Set a timer for 4 minutes. Given we are working at 60% of 1RM, the warm up may be brief (or in the advanced lifter non-existent).
Start the timer.
You’re done when you’re cooked or when the timer hits 4 minutes (example here: https://www.instagram.com/p/Bz-broqDVPc/).
Each week either add AT LEAST another rep and/or match the reps and add AT LEAST 1-2% to the load. Voila. You are getting demonstrably fitter with only 4 minutes of training. In 10 weeks you are 12-25% better.
This pro tip is more for the intermediate lifter, since it will require a good understanding of technique on any of your choice of large structural lifts (squat, deadlift, cleans, Olympic snatch, thruster, etc.) and a known or well-approximated one rep max (1RM).