I assume you're talking more bodyweight stuff rather than a squat rack in the garage?
I find the two easiest ways for me to get a killer heart rate going in this type of scenario is doing either a tabata, a death by, or an EMOTM.
in case you're not familiar. Death by, is similar to EMOTM but you add a rep each minute. for instance:
set your timer. minute 1 do 10 burpees
minute 2 do 11 burpees
minute 3 do 12 burpees
etc etc
I would either do that, or tabata, or an alternating death by if you had to do push ups or dips on a chair or situps or something because once you hit failure on the pushups you may sorta kill the workout. so maybe like
min 1
10 burpees
min 2
10 situps
min 3
11 burpees
min 4
11 situps
and so on. (even though I'm not a fan of situps).
just some simple ideas. if you have kettlebells or anything that weighs 35-50lbs+ (bag of concreate or sand???) you could throw in goblet squats with the same format.
tabata idea:
20 seconds on, 10 seconds off for 4 minutes
burpees
20 seconds on, 10 seconds off for 4 minutes
air squats
20 seconds on, 10 seconds off for 4 minutes
jump rope for reps
20 seconds on, 10 seconds off for 4 minutes
kb swings, or chair dips or whatever
.............just tossing out ideas. normally i program these types of wods to be accessories to what every my strength lift of the day was.