I’m assuming you lift at home? What equipment do you have? What type of surface do you lift on? Some things that come to mind:
Burpees
Complexes
Medicine ball slams
Plate/sled pushes
EDT - pick 2 exercises and do as many reps as possible in 15 minutes (15 minutes for each exercise). Squats+pullups, DL+pushup, etc. On the next workout, try to beat the number of reps from the previous workout.
Rope jumping and shadowboxing, along with a calisthenic circuit should do fine. You won’t necessarily make any gains, but you should be able to maintain easily enough. Try 8-counts for rounds of time, or whatever. Do you lift at home, or at a gym? If at a gym, I’m sure they would have something you could put together.