Agave syrup is virtually pure fructose. As a sugar alternative it's ... not that great. The insulin response is fairly low, true, but the high fructose content carries its own risks.

<https://www.healthline.com/nutrition/agave-nectar-is-even-wo...>

Stevia would be a non-sugar-based sweetener, though it does have a distinctly different taste.

I'd learned to drink coffee with milk/cream, no sugar. With decent beans (Trader Joe's Bay Blend, e.g., nothing fancy) and a Moka pot that's more than sufficient.