Eating

Picar (*) To nibble.
¿Hay algo para picar? Is there anything to nibble?

Papear (*) To nosh.
El papeo is "nosh" or "grub". From the word papo/papada, the bit of flesh under the chin.
Ya es hora de papear algo (*) It's about time we ate something.

Ir de tapeo (*) To go for tapas.
¿Por qué no nos vamos esta noche de tapeo? Why don't we go out for tapas tonight?

Drinking

Una birra (*) Slang for beer, borrowing the Italian word for it.

Empinar el codo (*) Lit. To straighten up one's elbow like a pine. To have quite a few drinks, referring to your arm's position when drinking.
A estas horas ya estará en el bar empinando el codo (*) At this time he'll already be at the bar having a few pints.

Beber como una esponja (*) Lit. To drink like a sponge. To drink a lot.

Tener un pedo, peo (*) Lit. To have a fart. To be in a state of drunkenness. Not to be confused with tirarse un pedo, peo (**) to fart.
Manolo tiene un pedo de mucho cuidado (**) Lit. Manolo has a very well cared for fart. Manolo's really drunk.

Estar pedo, peo (**) To be drunk.

Estar mamado/a (*) Lit. To be breast-fed. Another way to refer to drunkenness.

Echar la pota/la pastilla/la papilla (**) Lit. To throw out the pan/the tablet/the baby's puree. To be sick.
Ya echó la pota dos veces (**) He's already been sick twice.

Una resaca (*) A hangover.
¡Joder! ¡Menuda resaca tengo! Fue el puto vino de ayer (**) Bloody hell! I am so hungover! It was that crap wine yesterday.