If I could eat Tuna Avocado sushi everyday, I'd be a happy girl. :-) However, that's probably not a good idea. I threw this sandwich together for lunch yesterday, and while it's not sushi, it's pretty good!
Take on can of tuna, drained, and add as little mayo or Greek yogurt as you need to make it stick together. Slice up some avocado and cucumber, and assemble your sandwich on your favorite bread. I added provolone cheese, as well. :-)