NYPost’s embedded link says he had 1 shot. Bruuuuuuuuce fessed up to (at least) 2.
https://nypost.com/2021/02/11/bruce-springsteen-busted-after-one-shot-of-tequila/
doesn’t mention in either how it was “served”
You can serve your friends drinks at home but you’d still be the bartender.
bar•tend•er bär′tĕn″dər►
n. One who mixes and serves alcoholic drinks at a bar.