Plain Water:  10 - 20 minutes (though I don't see an issue with intermingling Holy Communion with plain water, and neither does the Church).

Not to nitpick here, and definitely not to cater to scrupulosity, but should we deliberately do something that would dissolve the Sacred Species?  But then again, there could be a case where someone with dry mouth could start getting choked, and it would be either take a sip of water, or allow a bad situation to become worse (possibly even coughing up or otherwise ejecting the Host).  Our Lord certainly foresaw that His Body would be in the form of simple food, and sometimes things such as this happen.  Besides, in the East (whether uniate or schismatic), the faithful receive simultaneously under both kinds, and somewhere along the line, both forms will disarticulate soon after being consumed, and cease to have their respective accidents.

The Orthodox have some strange ideas about receiving communion.  Not sure how close this is to mainline Orthodox thought, but here's a sample (to be fair, this is a Coptic Orthodox site, not Byzantine Greek Orthodox):

https://tasbeha.org/community/discussion/12494/after-communion

It all sounds almost тαℓмυdic.