Yes, it can be a trigger for some people. Some years ago, I had a seizure while having the flu. Afterwards, I visited my neurologist (epileptologist). She noted it was most likely due to dehydration. Triggers will also vary based on the type of epilepsy one has and anti-epileptic medications one takes.
Also, the electrolytes can become unbalanced when dehydrated. Electrolytes include Sodium, Magnesium, Potassium, Calcium, and Chloride. I also have hyponatremia, low-level sodium, somewhat due to a side effect from taking Carbamazepine (Tegretol). Other medications, such as diuretics, can also affect one's electrolyte levels. I have been admitted twice to the hospital due to my low-level sodium.
I would speak to one's doctor regarding individual cases, as every person is different. However, one thing I've learned after having epilepsy for 40 years is that it's essential for one's electrolytes to be in balance. This also goes for those without epilepsy. A standard blood test can determine one's electrolyte levels.
Bottled water is available with electrolytes as well as other beverages on the market. In my case, I have been put on medication when my sodium was low.
Good luck to all.. and keep hydrated, especially in this hot climate of our's.

I am on that med also, but with depekote too, I live in Colorado and it's a dry climate area here, I wake up during the night and get some water, a quick swig of it, and go back to bed, so I could not say if it's the meds or the the climate or both my opinion

Thank you! We think dehydration brought on our 2.5 yr Olds first seizure which ended in a hospital stay and diagnosis of epilepsy.

Yes! I have problems drinking water and I found it’s best that you do drink water and not too much caffeine especially sugary drinks. I found energy drinks are definitely a big no as well.