First suggestion I can suggest? Pack a reusable water bottle/canteen. After that, it's a matter of zeroing in on the coolers the Convention has around the space and rooms, as well as water fountains.
Depending on your cosplay, it would be prudent to designate a friend who isn't cosplaying as a handler of sorts- they make sure you hydrate regularly so you don't pass out, as well as note how much you're moving under it all.
For non-cosplayers, I suggest loose, light cotton clothing. Ditch the darker colors, as they absorb more sunlight as heat.
The convention center has been pretty cool for the times I came by (since 2015).