The miso soup won't have stopped your ketosis as it contains very little carbs.
Normally, you can have upto 30 grams of carbs per day and still stay in ketosis (some people can even have upto 50 grams, but that's not the case for everybody).
The juice of one lemon contains +/- 5 grams of carbs, so adding a bit of lemon juice to the water won't affect your ketosis either.