Anyone who knows me will tell you that I love my coffee. For years my go-to coffee beverage was Vanilla Hazlenut coffee flavoured with Amaretto Cream. Yum!
I haven't had one of those in years.
I stopped drinking flavoured coffee and creams when I started eating a gluten-free diet. I went cold turkey on the flavoured coffee.
Regular coffee from beans grown for a coffeemaker are gluten free. No problem there. It is when coffee beans start to go through processing there can be an issue.
Instant coffee should be avoided whether it is flavoured or not because both contain gluten. But not the case for all flavoured coffees. Some do contain gluten, but not all. In The First Year Celiac Disease and Living Gluten-Free Jules E. Dowler Shepard lists "flavo[u]red coffees and teas" as one of the common products that MAY contain gluten. This is where it is important to read labels. Not all companies chose to disclose if their products are gluten free whereas others may contain a gluten-free label. You can always call the manufacture's 1-800 number to further investigate.