Unfortunately, there aren't many drugs that come up as a false-positive for cocaine.
These include coca-leaf teas.
Topical anesthetic that contain cocaine (used often for nasal surgery)
And certainly if there is a concern that this is a false test -- then the second sample of urine is sent for the confirmatory testing, which is nearly 100% accurate.
Generally no prescription drugs will show up as Cocaine.
There have been cases where certain herbal "coca" tea will yeld a postive cocaine test.