Best is plain water. Try to avoid milk, coffee, tea, nescafe etc. I know of a man who drink lots of coffee and tea tarik everyday. Now he got diabetes and hypertension. Me : I only drink plain water everyday, at least 10 glasses. I very rarely  drink milk, tea or coffee. IF I'm sick like sore throat or cough, I don't take medicine, just plain water will do, and few days time I'm OK again.

When I travel, I always bring my bottled water just to keep me hydrated all the time.
I've seen many ppl who drink only 1 or 2 glasses of plain water  each day. Some are even worse. They hardly drink any plain water at all. Everyday...they only take milo, coffee, nescafe, tea tarik etc. This is commit suicide. Due time, because of the prolong constant dehydration. they will get fatal diseases like cancer, diabetes, hypertension etc etc.

When you get fatal diseases it means you have to suffer for many many years before you die.

The magic word here is REGULARLY. It is okay to drink coffee or milo etc once in a while but not regularly.
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