I usually stop drinking coffee once the weather breaks and switch to hot tea with lemon and honey in the morning before work/on the way to my area. Besides that I don't really have any one drink that I go to every single day. I will toss one of those lemon juice squeeze bottles in my bag and squirt some of that in ice water. Other times in the morning I'll make a couple half tea/half lemonades to bring. Sometimes I'll drink a Gatorade but I try to avoid drinking them too much and almost always keep it to a single 32 oz if I do choose this option. I definitely like to have an ice cold soda most days - Coca-Cola, Dr. Pepper, Sprite, and 7up are my gotos and for whatever reason Mt. Dew (the nectar of the tards) just tastes particularly nice in the summer to me.
I live in a very humid area, so in the mid to late afternoon heat it's usually straight water, half a bottle to drink, the other half to dump over my head when if it's a real blazer.
I definitely drink quite a bit of fluids each day in the summer though, regardless of the combo. If I don't, I really feel it the next day and my piss looks like brown mustard.