Thinly slice the cabbage (you can do this with a knife, food processor or mandolin) and place in a large mixing bowl. Add chicken and mayonnaise. Remove 3 to 4 jalapeňos from the can, slice into rings, and add to bowl. Remove the onions and carrots from the can and chop into ¼ inch pieces (you'll have about 1/4 cup). Add to cabbage mixture along with 3 tablespoons of the canning liquid. Add the cilantro, stir everything together, taste and season with salt, usually about 1 teaspoon.
Wrap tortillas in damp paper towel and place in an unsealed ziplock bag. Microwave at 100% for 1 minute, then let sit 1 minute before serving.
Immediately spoon about 1/3 cup of the cabbage mixture into warm tortillas and serve.
Cook's notes: This dish can also be made with Brussels sprouts. Here's the recipe for that version.