In a medium mixing bowl, whisk together the mayonnaise, sriracha hot sauce, white vinegar, and granulated sugar until smooth. Add lemon juice and whisk again.

Gently shred the imitation crab into thin strands with your hands or a fork and set aside.

Julienne the cucumber and carrot into thin, uniform strips.

Pat the julienned cucumber dry with a paper towel to remove excess moisture.

Combine the shredded imitation crab, dried cucumber, and julienned carrots in a large bowl. Pour the dressing over the mixture and toss gently until coated.

Transfer the salad to a serving dish, sprinkle panko crumbs on top, and optionally add sesame seeds. Chill for at least 1 hour before serving.