"Anti" exercises challenge your core's ability to resist (in this case) rotation. They're highly useful in both injury prevention and sports performance training. Think of MMA, where your ability to resist an opponent twisting and throwing you around like a dishcloth has its benefits.
Here's an advanced anti-rotation exercise using a landmine:
Landmine Squat Anti-Rotation
Decide if you want to squat or not.
You can do these in a standing and fully-upright position to make them easier. Adding a squat does nothing to load the squat pattern itself. Instead, your hip mobility and stability is further challenged and you'll need to work harder to switch on your hip stabilizers to stop your knees and hips collapsing. Also, it's just plain difficult.
Make sure the bar moves, not you.
Stay locked in and tight. This means your arms are allowed to move the bar left to right, but your job is to resist going into rotation. There might be a little movement, especially if your biceps hit your pecs a little early on, but the point is to resist.
Get 360 degrees of air.
It's pretty hard to breathe during exercises like these. For this reason, you're better off taking short and sharp breaths every time the bar moves to one side. Get yourself ready and imagine filling your midsection with 360 degrees of air around your spine. Try to create high levels of intra-abdominal pressure throughout.