Tomato Ketchup
I have an Australian friend whose family used to eek out the last dregs of the tomato ketchup by adding milk.

MILK?!
(Mean Mad Mutski, Wed 29 Oct 2008, 11:52, 14 replies)

everyone knows
that you should use a judicious amount of vinegar
( Vipros. clever got me this far, then tricky got me in, Wed 29 Oct 2008, 11:55, closed)

?!
VINEGAR?!
(Mean Mad Mutski, Wed 29 Oct 2008, 12:00, closed)

Vinegar?
I use whisky.
( Cawl, Wed 29 Oct 2008, 12:16, closed)

weak
I use blood

edit: damn the librarian!
(Halfy By light alone, Wed 29 Oct 2008, 12:24, closed)

Muahahahaha
hahahahaha.

And I'm an examinations coordinator now. I've hung up my stamps.
(GONEism, Wed 29 Oct 2008, 12:38, closed)

Blood?
You suck, Halfy.
( Cawl, Wed 29 Oct 2008, 12:51, closed)

oh dear god
thats awful!
(Halfy By light alone, Wed 29 Oct 2008, 14:02, closed)

Yeah...
But you love it.
( Cawl, Wed 29 Oct 2008, 14:04, closed)

whisky is an acceptable substitute
you will find however that ketchup (if memory serves) has a vinegar element anyway, and you should only need a tiny amount
( Vipros. clever got me this far, then tricky got me in, Wed 29 Oct 2008, 13:53, closed)

We used to add water.
I don't do it to tomato sauce any more, but I've been known to add water to the dregs of a jar of pasta sauce so I can the last bits out.
( argyleblanket The man on the roof works for me, Wed 29 Oct 2008, 12:16, closed)

To be fair,
If you're cooking something like chilli, and using tinned tomatoes, then it's good to use water to rinse the tins 'round, as it'll cook off anyway.
( Cawl, Wed 29 Oct 2008, 12:20, closed)

Add blood.
Innit.
(GONEism, Wed 29 Oct 2008, 12:21, closed)

Or you can warm it in the microwave
if it's going on chips.
(Juan Quar is clinging to her front teeth on, Wed 29 Oct 2008, 12:24, closed)

I have no idea why
But this makes me think of the following Colin Mochrie and Ryan Styles dialogue from Whose Line is it Anyway...

Ryan: Hey Col!
Colin: Hey Ry!
Ryan: Say col, what do you like to put on your tacos?
Col: Haha, why, a little bit of paper.
(GONEism, Wed 29 Oct 2008, 14:00, closed)