If you're looking to add cardio to increase your endurance for a sport, like BJJ, you should do jogging/swimming. Boxers and MMA fighters have to do road work, AKA running, as part of their training. If you have a regimented practice, you would do your road work in the morning, then your training later in the day. Typically, these runs are not very long or done at a breakneck pace because you want to be fresh to focus on your sport.
Examples would be to start jogging in the morning, working up to about 3-4 miles at a moderate pace. That cardio foundation would support your BJJ practice. If you want to do endurance workouts as stand-alones on some days, you can add TEMPO runs or sprints. Other options are sled drags, plyometrics, and agility drills.
To sum: Jogging in the AM as part of your consistent routine when training. More demanding sessions on days you're not doing any BJJ if you want to elevate your endurance further.