a standard 'shot' 1.5 oz in America is 9 teaspoons of measured liquid.
A typical frosting recipe calls for 2 teaspoons of extract. For ease of math let's just say 8 teaspoons is a shot - err conservatively also.
Let's go with 40% alcohol in extract. A shot of 40% alcohol - 80 proof would provide 3.6 teaspoons of pure alcohol.
However, 2 teaspoons of extract at 40% is 25% of 40% of 9 or 8.
That comes out to .8 of a tsp of alcohol diluted and spread out over a whole cake. Let's assume you get 8 slices from a cake. That is 1/8 of .8 of a teaspoon of alcohol ingested. Or .125 of .8 of a teaspoon of alcohol. That is .1 of a teaspoon of alcohol per slice of cake.
I'm guessing one would have to eat a hundred pieces of cake to catch a buzz.
You can have your cake and eat it too.