What are the most eco-friendly coffee cups?

We LOVE that you are wanting to learn how to be more eco-friendly, that is why you ended up here, right?....
As you probably already know, there is so much plastic and non-recyclable materials used in single-use coffee cups. We know it is easy to slip into buying a coffee with single-use plastic on the way to work or school (I don't know about you but we would rather be abroad, enjoying a coffee with a lovely view but we all have to work - unfortunately!). Now what if we stopped choosing single-use plastic cups and started using a more eco-friendly products?
Many are turning to titanium coffee cups or ceramic coffee cups.
Ceramic coffee cups
Ceramic coffee cups are not thermal so they do not keep in the heat or cold temperatures of the drink inside. Ceramic takes many years to decompose as well and they also tend to be made with silicone lids which take even longer to decompose. Another disadvantage to Ceramic coffee travel mugs are more fragile so it can easily break.  Making this not a very good option.
Titanium coffee cups
Titanium coffee cups are great as they are great for insolation purposes as they tend to be double-walled which means they keep in either the warmth or cold temperature of the drink inside. However, titanium takes 500+ years to decompose. This means that with each metal bottle we buy, it has a lasting affect for many years. 
Bamboo-fiber coffee cups
Bamboo-fiber coffee travel cups are not double walled so they do not have the same thermal abilities as double walled titanium coffee travel mugs. Nevertheless, Bamboo is a natural isolator so there is more insolation capabilities compared to ceramic coffee travel cups. The huge benefit to bamboo-fiber is that is will start to decompose within a year of being in soil (landfill). This does not mean you only get a years use out of the product. We recommend you use this product for about 5 years before replacing it. 
In terms of the environmental impact of coffee cups, the clear winner is bamboo-fiber which is why we chose this material above all other options.
Where can I get discount for bringing in your own cup?
Starbuck: 25p off
Costa: 25p off
Pret et Manger: 50p off 
Greggs: 20p off
Cafe Nero: Double stamps (not during covid times)
Tell us your thoughts?....