Quaff

Keyboard commands
~	!		@		#		$		%		^		&		*	(	)	_	=	+
	Q		W		E		R		T		Y		U	I		O	P	{	}	|
	q		w		e		r		t		y		u	i		o	p	[	]	\
		A		S		D		F		G		H		J		K	L	:	"
		a		s		d		f		g		h		j		k	l	;	'
			Z		X		C		V		B		N	M		<	>	?
			z		x		c		v		b		n	m		,	.	/
	q		w		e		r		t				u	i		o	p	Alt
		a		s		d		f						j			l	Alt
							c		v				n	m			?	Alt
		A			C		R		T				O					Alt
a		c			d		o		p		r		t			[		Ctrl

Quaffing, done by hitting q, means drinking. Most often you quaff a potion, but you may also quaff from a fountain or from a sink.

Quaffing a potion of invisibility obviously makes you invisible and so on, but with fountains and sinks the results may vary greatly. For example, quaffing from a fountain may release a water demon that may grant you a wish, but it might also just summon an endless stream of snakes. If you quaff from a sink, you may find a random ring, but then again you risk creating a water elemental instead.