EtG(Ethyl Glucuronide, a bio marker of alcohol)) is quite sensitive test. you will need to drink lot of liquids( either water or crane berry ) at least 6 -8 drinks in 40 hours. That is how it will dilute the biomarker level to the minimal possible point.But still it may not show as negative when urine will be tested.
It also depends how much you have drunk alcohol as more higher levels may take around 70-80 hours to get clear.
Because of its sensitivity, ETG will still show up as positive even if you try too much craneberry juice in short time.
It does not measure the level but it just tells you whether or not there is or was alcohol in blood recently .
It may become positive even if someone is expose to some daily use alcohol in product like lotions hand sanitizers etc.
I am enclosing a link with details about it and hopefully it will be of help to you.