Combine the vinegar, sugar and salt together in a large bowl. Add the cooked rice and stir together with the vinegar mixture. Set aside.
Use a vegetable peeler or mandoline to finely slice the carrots lengthways into long, curly strips.
Cut the cucumber in half lengthways, and then finely slice each half on the diagonal.
Scoop out the flesh of the avocado and dice into 1cm cubes. Place in a small bowl with the lemon juice. Stir gently to combine.
To make the mayo: combine mayo, sriracha, sweetener and sesame oil in a small bowl. Stir well to combine.
To make the tofu: Coat the tofu cubes in flour and pepper. Heat oil in a frying pan. Once hot, add tofu and fry until lightly browned on all sides. Add soy sauce and sesame seeds to pan and cook for one more minute. Remove from heat.
Assemble the bowl: Divide the vegetables, rice, nori and tofu across 4 bowls. Arrange each ingredient alongside the next to create a beautiful, colourful sushi bowl. Top with pickled ginger and mayo to serve.