Prepare the ingredients as instructed above.
Sushi rice: Wash and rinse the rice until the water runs clear. Drain well. Cook according to package instructions. Once done, season with rice wine vinegar and cover with a damp cloth to prevent drying.
California roll – Cover a bamboo sushi mat with plastic wrap. Place a sheet of nori, shiny side down, on the mat. Wet your fingers and spread the sushi rice evenly over the nori. Arrange crab, cucumber, and avocado across the bottom edge. Roll the mat tightly over the filling into a cylinder pressing gently to make sure it stays compact and tight.
Spicy tuna roll – Mix the tuna, sriracha, mayo, and scallions in a bowl. Place a sheet of nori on a bamboo mat covered in plastic wrap, shiny side down. Spread sushi rice evenly and sprinkle with sesame seeds. Arrange the tuna mixture across the bottom edge. Roll the mat tightly over the filling into a cylinder pressing gently to make sure it stays compact and tight.
Iced matcha latte: Whisk matcha powder with hot water until smooth and foamy. In a glass, mix water and sugar to desired sweetness. Pour in milk, then the matcha. Stir well. Pour over ice to serve.
Wet the blade of a sharp knife and cut each roll into 6–8 pieces, cleaning the blade with a damp cloth every few cuts.
Serve the sushi with optional wasabi, pickled ginger, and soy sauce. Enjoy with iced matcha latte.