Kettlebell swings are awesome for conditioning. Also give you plenty of hip thrust power which is key in BJJ (think explosive bridging, popping opponents off you from mount/sidemount).
They're low impact, can do 6mins intervals 2x a week and get big results.
The downside is, yes, expensive. But you can get a few months of progress out of a single bell. E.g. buy one you can just barely do 20 reps on, work up to intervals of 30sec swingining/30 resting, then eventually just do like one long continuous set of 150+ reps.
For grip strength/endurance: if you deadlift in your routine, just do some of the sets with no straps. That's enough for grip strength and endurance, particularly applicable to holding a gi in BJJ.
They're low impact, can do 6mins intervals 2x a week and get big results.
The downside is, yes, expensive. But you can get a few months of progress out of a single bell. E.g. buy one you can just barely do 20 reps on, work up to intervals of 30sec swingining/30 resting, then eventually just do like one long continuous set of 150+ reps.
For grip strength/endurance: if you deadlift in your routine, just do some of the sets with no straps. That's enough for grip strength and endurance, particularly applicable to holding a gi in BJJ.