Rinse the sushi rice well. Cook according to package instructions. Allow to cool.
Microwave the ¼ cup rice vinegar. Add the sugar and salt. Stir to dissolve. Pour over the sushi rice and stir the mixture in. Set aside the rice to finish cooling.
Shred the tofu with a block grater. Add vegan mayo, sriracha, soy sauce, rice vinegar, and salt to taste. Stir to combine. (This can be prepped ahead of time and holds well in the fridge!)
If using a bamboo sushi mat, cover it with plastic cling wrap. This helps keep cleanup easy. Prepare the sushi nori by slicing off a little under 1/3 of the horizontal length. Making it smaller will prevent oversized/overstuffed rolls.
Place the shiny side of the nori face down. Place a bowl of water nearby to dip your fingers into, which will prevent fingers from sticking to the rice.
Place about 2/3 cup of rice on the nori. Dip your fingers into the bowl of water and spread the rice using your fingers in "tickling" motions. Spread the rice uniformly to the edges of the nori, except, leave ⅔ of an inch empty at the top horizontal edge of the nori farthest from you.
On the edge of the nori closest to you, assemble your tofu, cucumber, carrot, and/or avocado. Make sure not to overstuff the roll with too many ingredients or it won't roll nicely.
Use the bamboo mat to tightly roll the sushi. Use a dab of water to close up the edges of the nori at the very end. Slice the roll in half using a sharp, damp knife. Rinse the knife and/or use a wet cloth between slices to keep the knife damp which will prevent rice from sticking and keep the cuts clean.
Continue slicing in half until you have 8 one-inch pieces. Repeat this process approx. 4 times until you have used up all of the rice and made a total of ~5 sushi rolls.
Serve and enjoy! I serve this with soy sauce, sriracha mayo, and pickled ginger.