I do this sometimes - I normally do stick to the sashimi and find that the soy and wasabi doesn't knock me out of ketosis. I also have a green tea and a bowl of miso soup normally. I'm a bit wary of anything else - the teriyaki contains a lot of sugar, and ponzu sauce is flavoured with lime / lemon so the citric acid might knock you out. Even the edamame which I love is quite starchy and might boot you out of ketosis...