Green’s Dictionary of Slang

blow (one’s) cookies v.

1. to vomit [blow v.1 (2b)/SE blow + cookies = food consumed].

[US](con. 1950s) H. Junker ‘The Fifties’ in Eisen Age of Rock 2 (1970) 99: Heaving, tossing, blowing your lunch (cookies).
[US]P. Conroy Great Santini (1977) 404: You got to have a light meal, otherwise you’ll blow your cookies all over the place.
[US]P. Munro Sl. U. 39: If you’re going to blow cookies, get out of the car.
[US]S. King Dreamcatcher 77: I thought he was going to blow his cookies when he leaned forward.
Wash. Toast.com [Internet] The two bottles of Jack that I drank [...] was really starting to work on my gut and it was not long before I was looking for a place to blow my cookies.

2. to reach orgasm [blow v.2 (1b)].

M. Whittemore ‘Little Billy Burlap and His Dog Butt-cheese’ Part Seven at NaughtyStory.com [Internet] Billy was getting extremely close to blowing his cookies, sitting there naked, polishing his rod, watching two girls getting off on each other.
D. St Martin ‘A Visit From Sis’ on White Shadow [Internet] Feeling the gorgeous nymphette coming was the last straw to Roberta. The mental image of the beautiful young teenager blowing her cookies in sixty-nine above her own voluptuous form was too much for Roberta.