A good one I've learned is salt or atomic warheads. It gets your mind out of fight or flight mode. Also, do the five senses. Five things you can see, four things you can hear, three things you can touch, two things you can smell and one thing you can taste. I've tried all of these and they work really great. I've even helped friends with these techniques

If possible, I always try to grab something cold from my freezer. I look like an idiot and honestly that's part of why it works. I'm just standing next to my fridge holding a bag of frozen peas, or even just an ice pack. The cold helps to ground me and the realization of how silly I look gets me to start laughing

I have a rice sock (for my migraines) that I fiddle with when my anxiety gets bad!! Also deep breathing helps (sometimes) and going outside. Sending good vibes!!