will synthetic urine like the golden shower enhancer for example show up as an adulterant with on-site urinary drug testing cups? will the synthetic urine show up at all as a positive with these drug cups?
It wont show up as an adulterant, but if the synthetic is expired, stored improperly (ie; exposures to direct sunlight) or otherwise a bogus product with no creatinine, it would be ruled as a sample "not consistent with human urine (aka "substituted specimen") if the EZCup test has integrated checks for creatinine, pH, specific gravity, etc.

Some online medical supply distributorships such as Craigmedical, Meditests, etc. offer EZCup test kits with the integrated validity checks as well as the original 5 drug EZCup kit.