Why do you have to take tablets with water?
The tablets I'm on at the moment are to be taken with a glass of water, why not a cup of tea or a glass of lemonade? Does it make any difference?
Some liquids may make some pills dissolve too fast which can cause problems with either releasing the dose too quick or give you heartburn (or ulcers in extreme circumstances). some liquids may reduce the effects of some pills.
Of course, some pills may be perfectly OK to take with some other liquids, but it would be to much work to list which liquids are OK to take each pill with and which ones should be avoided so they all say take with water to be on the safe side.
Basically it doesn't matter one jot BUT avoid citrus drinks (pineapple, grapefruit) as they MAY interact with certain drugs, e.g statins and certain BP lowering tablets.