I admit, I am better at horizontal activities than I am at vertical ones.
That's unfortunate - a glass on its side would have to be entirely empty. Barring a sippycup lid, of course. Or perhaps the vacuum of space. Or the glass' contents being solid or gaseous rather than liquid. Or if the sideways glass was just relative to the room that contains the glass, such as might be the case with a tipped-over tornado-ravaged trailer. Or it was at the whim of capacious amounts of lateral kinetic energy, forcing its contents to remain inside. And if any of those are the case, then I daresay there might be more pressing matters than the glass.