I've seen hummingbirds visit and revisit feeders in which the sugar solution has fermented. Their flight patterns change after a few visits.

And they no longer hum, but sing the words right out loud:

"Goddamn them (hic!) all!
I wash tol (hic!)
We'd cruish the shes fer 'merikan golt...."

Well, anyway, they do seem to enjoy their little tipple.