hey what workouts did you use because i don't have any weights either and i've been trying to think up a good circuit under those conditions
I just alternated between legs, varations of push ups and then abs.
1 X variation of a squat, or jump, or leg raise
1X Variation of push up (spider man, frog, T-push up etc)
1X Variation of sit-ups (In & outs, crunches etc)
repeat until you reach 10X.
That means in total I did 3X abs 3Xpushups 3Xlegs.
I also tried just setting a number. Ex. 20 squats instead of 30 secs
after doing 1 set, I would add a 400 meter dash (60-70%) then take my 1 minute off.