Perhaps in an obsessive-compulsive ritual, OPs first instinct is to lock his lips around the edge of the glass wherever it may lie, then lower and rotate his head in synchronicity with the rotation of the glass, so as to conserve the liquids gravitational potential energy for as long a possible.
All this glass rotating isn't really common practice. Not that it can't be done.
I thought OP was odd for centering his frame of reference on the liquid in his glass, rather than the surface of the Earth, so that the entire planet bobs up and down every time he takes a sip.
But here's you revealing that you drink from upright glasses: I guess you lap it up with your tongue like a dog. Are you a dog? Rotating glasses is a lot easier with the human finger + opposable-thumb combo.
@ScorpioGlitch This dog thinks you're a dwarf. Is that true?
In OP's scenario, he's clearly a midget swiping clumsily at a glass on a bar or table far above him.