Is cold coffee has any bad effect specially in NIGHT ? If yes , then whats the alternative which though healthy also ?

It's summer going on here . After Gyming , i want to cool down my body so that i can study late night** and this summer is also my reason that i dont want to take hot coffee.

but there is one physiotherapist who said that it will affect my intestine or create other problem also if i use it for long time.

***the thing is that i started using cold coffee at night from may' end week and will use till august' first week ?***

so please help me in this case and also provide me a alternative that keep me on running through night and that should be summer cool and healthy(m a diet conscious) .