Today is again nice and simple for your workout.
3 minute interval training.
You can do this workout either running, cycling, swimming, or rowing. Choose whatever format you like.
You are going to be working for 3 minute intervals and using a 3 minute recovery between these. So, each interval will total 6 minutes. The aim is to complete 5 intervals in total, so that's 30 minutes of total work.
During the work intervals you should be working hard, but remember you have to go for a full 3 minutes so pick an intensity that allows you to complete the time without having to stop halfway through. Start out steady first couple of intervals so you can gauge your level. Working at a level of about 6-7 out of 10 is probably going to be about right.