There are loads of threads on ideas on how to flavour Huel. I have linked below to the biggest one. There is also a recipes section on the Huel main website.
I’ve had plenty of Huel milkshakes, they work great.
The Huel flavour pouches contain the sweetener Stevia and some people dislike the taste that can leave. I do use the Huel pouches but don’t be afraid to find your own way. 100% organic Cacao powder is nice. I often have a Vanilla Huel with a big teaspoon of Cacao powder in the morning.