Cook sushi rice according to package directions.
Stir together vinegar and sugar. Stir into the rice and allow to cool.
Stir together Sriracha and mayo. Refrigerate until ready to use.
Cut the nori sheets into three equal pieces. Lay out one strip of nori shiny side down.
Add 1 to 2 tablespoon of sushi rice onto the left side of the nori.
Press into a rough square. Spread on some spicy mayo. Top with a slice of salmon, several cucumber pieces and a slice of avocado.
Fold the bottom left edge up over the fillings, forming a cone.
Continue rolling into a cone shape.
Secure the edge with a grain of rice.
Repeat with remaining ingredients.
Serve with soy sauce, wasabi and pickled ginger, if desired.