Generally you'd mix some drinking water in or remineralizer so it contains some minerals rather than none at all.
If you think about it though, generally rabbits wouldn't actually drink much water. They'd get all their water requirements from the plants they eat. So if the rest of the diet is correct it shouldn't be necessary to add extra nutrients via water, everything should come from the food.
So, another way to help resolve it is to increase the amount of fresh plant matter - grass etc. in your rabbits diet. They'll then drink much less water anyway.
If you think about it though, generally rabbits wouldn't actually drink much water. They'd get all their water requirements from the plants they eat. So if the rest of the diet is correct it shouldn't be necessary to add extra nutrients via water, everything should come from the food.
So, another way to help resolve it is to increase the amount of fresh plant matter - grass etc. in your rabbits diet. They'll then drink much less water anyway.