I have loads that I rotate;
500m row sprints resting 1 min - you gotta work up to this. start with 2mins rest. I'll usually do 8 total rows
200m rowing machine sprints with a 1-2min rest x10-15 total sprints
Wattbike or spin bike - 45 sec sprint as fast as you possibly can, then active rest for 3min45sec. One 4min round = 1 rep, do 6-10 in total
Spin bike; 10mins on 45sec sprint + 15 sec slow, then 10mins 30 sec sprint + 30sec slow recovery
I have one I do once or twice a week, just depends. It's basically a barbell complex of; deadlift + hang clean + half/jump squat + push press + romanian deadlift + row, then 3mins of hard cardio(for example, if I do rowing, I'll do 750m as fast as I can). You can use skipping or cycling. If you cycle, you to get 2km as fast as you can. The complex + cardio is 1 set, and I do between 4 and 6 sets per session with just 40kg. 40kg is plenty, it's more about getting through the work. It's hard to explain, but this last one always gets me super fit, without necessarily losing weight/muscle like if I just ran myself into shape.
These are all workouts I used to do playing rugby 7s. That's the best shape, that I've ever been in.