What about an aperitivo in country-style while being in the city-center?
That’s what GUD in City Life offers you. Actually, GUD is a good choice for lunch or a break during the afternoon too.
I personally like it for an happy hour, the atmosphere is really good: you are surrounded by nature, even though you are in the center of Milan. Also, you can either decide to sit at a table or go for a chill mood and sit on a beach chair.
As for drinks, there is a wide choice of both soft and traditional drinks; one you order your drink, they give you a pack full of really good popcorns too! Of course, you can order some other food; for instance, I ordered focaccia with prosciutto and burrata and a bowl with salmon and avocado.
While I really liked the spot and the idea, I didn’t really appreciate the fact that there was no table service, or at least this happened to me on Tuesday. 
Finally, keep in mind that if you want to book a table, you have to be a group of at least 4 people