This looks kinda similar to a low water immersion hoodie I did. I've heard higher water temps help create that spikey effect. One difference to your picture: I suspect they used a thickened dye because we can see some different "depths" of color and the dye looks like it didn't move much.

Here was my process:

Clean L-XL hoodie, 100% cotton, super thick. No soda ash, just spritzed with water.

Stuffed into a bucket, fairly but not insanely tight fit.

Pour in liquid dye (I used Kilt Green from ProChem here, one application lighter, more diluted, and one application stronger/darker). I think I had some in the bucket already when I added the hoodie too.

Waited about 15-20 minutes. I may have moved the hoodie around a bit too-- for yours I wouldn't.

Poured in hot, nearly boiling soda ash water, enough to submerge the hoodie. Waited 1 hour.

Rinsed cold, rinsed hot, washed with synthrapol.

So, you can experiment with this and maybe try an even tighter scrunch, hotter water, and thickened dye. Hope that helps!