Heat the chocolate shake if you drink it. What about making the coffee weaker. Have weak tea, black, green and peppermint. I had the same bother aand started having warm water when i was too cold to manage cold water. This also a good habit to form for post tfr.
You could also rinse your mouth well after drinking the coffee, i'm not a coffee drinker but black tea caused the same problem.
I tried the Vanilla Shake with coffee this morning just to change from the tea but defo going back to tea. havent noticed anything on my teeth yet but i listerine the hell out of them three times a day so maybe thats helping a small bit
I am not drinking tea or coffee whilst on LT as I cannot stand T without milk serves me right i suppose for being fussy haha, However after getting tips from the sight I am looking forward to doing my self a mint hot chocolate yummy I am 3 days in so I think I will give that a go tomorrow