Over the last few years, sled exercises have become increasingly popular. Sled pushes for example, are great because there isn't much of a learning curve and really hard to have incorrect form.
You can add sled exercises into your routine as a steady state cardio day or for max effort anaerobic training. Personally, I enjoy using medium weight and moving it as fast as I can in sprint intervals.
If you do not have access to a sled or want a challenging alternative, give these max effort wall pushes a try. You can do these from anywhere and you can use any stable structure (tree, car, bench, etc).
Aim to push as hard as you can for 30 seconds. Rest for 90 seconds and repeat for 3 total rounds. You can switch up your stance and foot positioning throughout or keep it the same.