Smelling Salts do not work in PVP. You could use Sleep Ward potions but people rarely do.
If you have a competent BLM the healer will be slept for 21+ seconds no matter what. The opening 30s Sleep will be purified but the BLM can Swiftcast Sleep forcing a 15s unbreakable sleep (barring teammates hitting him). With 2s left the BLM can begin casting Sleep again which will last another 7.5s.
Finding a competent BLM is easier said than done however.