Yes, I did that for a short time. I kinda liked it, but I didn't like how it gunked up my my coils and wicks, presumably due to the sugars in lemon juice. I then tried citric acid primarily as an alternative to lemon juice. Now this gunking effect needs to be put in context. I vape a lot of unflavored juice, which is intrinsically easier on wicks and coils than any flavored juice. Adding a bit of lemon juice to unflavored certainly doesn't produce gunking as bad as say, a NET. Oh, I was using 1 drop per 10ml.