Some use this method, I did once and over did it a bit with 6 lemons in one day, which made me rush to the toilet a lot!
If you need to use lemon juice try and keep it very sparse, but in my view it has its price, it makes you get a taste for food again.
I have used lemon juice towards the end of a fast when the taste in my mouth was bad, but I usually ended up breaking the fast shortly after using the lemon.