This course should teach a bit slang Hindi. This is common. The synonym of 'paani' is 'jal' or 'neer'.
I guess the course's aim is to teach words that are most relevant in everyday speech. Barely anybody uses 'जल' or 'नीर', and teaching those words would probably give new learners too much to remember.
Jal isn't used much at all unless you're watching 'Vivaah' and that word comes up 50 times
Or if you are speaking of Ganga jal. ;)
The vocal should be mutually comprehensible by "Urdu" speakers.
slang hindi is as dynamic as two chemicals mixed together...
it changes forms, words, with every 100 kms in India.
Would a water glass then be एक पानी गिलास, or would you have to say "a glass for water?" And how would you say "a glass for water?"
Likely "एक पानी का गिलास"