Renal physiology: why does drinking four cans of artificially sweetened caffeinated energy drinks ...

My question involves someone who has become dehydrated after drinking four cans of artificially sweetened caffeinated energy drinks. She has a very high blood sodium level, low blood glucose level, low blood pressure and high heart rate. I don't need to explain every abnormal result, just the mechanism that caused dehydration.

I've found that caffeine is a diuretic which increases renal blood flow and inhibits Na+ and Cl- reabsorption in the nephron. At first, I thought this is what lead to her dehydration, as the increased Na+ loss would increase water loss. However, I'm not sure why her sodium level is so high (310, instead of the normal range of 135-145) if caffeine is inhibiting Na+ reabsorption. I'm really not sure where to go from here but I do have a decent understanding of the content I'm studying, so a little nudge in the right direction should be all I need (hopefully!). Thanks for any assistance!