Tuck jumps, my friend.
Very easy and will dust you fairly soon.
Start off in a low squat, jump up explosively and bring your knees to your chest, upon landing, absorb the impact by going into another low squat and immediately jump again. Do as many as you can for as many sets as you like. These are pretty demanding, and I feel it in my quads more than when I sprint so see how many you can get away with. A good starting point is 3 sets of 10 jumps.
The important part is to do these rather fast, without getting sloppy, youtube only has shit videos so I can't show you a good example unfortunately. Also, do these barefoot, so you don't land so hard (since shoes give the false sense of protection, so you feel more confident to smash down) ...