Of course there’s running, jogging, and walking, but you might want to change it up! I love to dance around my room to music I enjoy, but you could also do knee-ups, burpees, and the classic jumping jacks!
Too many to mention. I usually use Nike's Training app, it allows me to set parameters such as equipment or none, length of exercise, and intensity. The data is synced to my Google fit account via my smart watch.
You can do aerobics and you can go out for running. You can also go up stairs many times. That last thing is something I do a lot to train for mountain climbing.
Dancing can be very accessible and as active as you need it to be. All you need is a way to play energetic music and some space.
I like to dance, so I'll use a dance video or game to do some cardio, especially if it's cold or raining outside. Walk/jog combo is also not bad when it's nice out.
Running. One of my favorites to do- 100 jimping jacks, 90 crunches, 80 squats, 70 leg lifts (35 each leg), 60 jumping jacks, 50 crunches, 40 squats (20 EACH LEG), 30 jumping jacks, 20 crunches, then run 1 mile or run 10 mins
If you're living in an apartment, choose a floor, climb up and down twice or thrice. That should give you enough of a cardio to begin with.
I do HIIT workouts from YouTube. I'm also doing the couch to 5k. Neither require special equipment and both are sustainable