Smashburger downtown offers very adult milkshakes
While Smashburger has had beer on its menu since the Denver-based chain got its start, the store that opened last fall in the Tabor Center also serves alcohol-spiked shakes and floats ($5.99) that are the perfect bad-behavior ending to a quick burger and fries.
I love a Guinness Float, and Smashburger's version is fine (really, how could you screw that up?), but both the Top Banana, made with DeKyper Creme de Banana, and the Malibu Shake, made with Malibu Coconut Rum and vanilla, chocolate or strawberry Haagen-Daz, give a nice tropical twist to a burger dinner. There are also versions made with DeKyper Creme de Menthe and Lazzaroni Amaretto, among other alcohols (vodka most definitely predominant).
And ignore the name: "After Hours Shakes" are actually available all day at the Tabor location (and the Tabor location only), so if you're having a bad day at work you can take a quick break, treat yourself to a Mo'Joe Shake made with Kahlua and vanilla or a chocolate Haagen-Daz shake, and go back to work with a little more mojo.
And not that much guilt -- for some reason, it seems a little less questionable to have a milkshake at lunch than slug down a martini.