Staying hydrated has two parts. Drinking enough water and maintaining electrolyte levels. There are seven major electrolytes
If you drink excessive water you will leach electrolytes. If your blood sugar is high you will dump glucose in your urine and leach electrolytes. In fact the drop in electrolytes is one of the complicating factors in DKA and that is why you are put on an IV even though you may be drinking lots of water.
And the real concerns is that it is well known that low sodium levels in fact make you insulin resistant. Sodium turns out to have a significant role in glucose uptake. So going low on sodium could at least partly explain the insulin resistance.
So my suggestions is to not drink just water but instead focus on getting re-hydrated through drinking electrolytes drinks such as PowerAde Zero which contains Sodium, Potassium, Calcium and Magnesium. You can also take supplements. I take in extra salt in my diet as well as taking Potassium and Magnesium supplements.