(Lorelai and Rory ring the doorbell. Emily answers the door.)
EMILY: Hello, hello, hello.
LORELAI: Wow, Mom, hi. (to Rory) Uh, check the rubbing alcohol.
Rubbing alcohol is an American term for those types of alcohol, such as methylated spirits, which are used as an antiseptic in domestic and industrial uses. They are often used as cleaning products, and their name comes from the fact that in the past, they were used in the same way we use heat rubs, to relieve pain and stiffness.
Lorelai appears to think her mother seems so cheerful she must be drunk, but in fact you can’t drink rubbing alcohol – they put bitter poisons in it to stop people abusing it that way. It would taste awful, and you would most likely become very sick before you got drunk. Lorelai is just joking though.