Magical Barkeep

The Game:
It is a fun concept, but still lacking in some points. There currently is no risk in the game, you just make drinks and earn money indefinitely, and the money doesn't even do anything. If you need some advice/ideas on what it could do if you were to turn this into a full game:

• Easiest route, make it an arcade like game. Put a time limit on it and make it so you have to get as much money in that time as you can.
• Otherwise, making the ingredients you have limited and adding individual days. At the end of each day, you could then use the money you made to buy more weird ingredients which you have to guess what those may taste like, giving you the chance to be more efficient by requiring fewer ingredients for the same taste combination.
• Third possibility, making upgrades you can buy. (Though this is boring in my opinion)

That said, it is clear to me that you haven't made a lot of games yet. And perhaps you may be best of just turning this into an arcade like game and moving on learning as you make more small games, slowly rising the bar as you go on.

Additionally, it would be nice to have some reaction from the customers when they drink it, as a way of additional feedback for if they liked it or not. Even if the change in gold is already some feedback for the player if they did well or not, having additional feedback is good and makes the game feel more alive.

The Art:
Can still improve, but don't worry about it, as it will do so naturally just by making more, especially this early on.
In Godot in your project settings, at: General > Rendering > Textures > Canvas Textures > Default Texture Filter, use Nearest instead of linear. It will prevent the color bleeding between pixels.
At: General >Display > Window > Stretch > Mode, use viewport to have everything scale up and remain in the viewport as shown in the Godot editor. Right now, resizing the view lets you see outside your scene, which would be fixed by this.

(Small thing I noticed in the GDD, you forgot to replace the part "Gameplay overview" with the gameplay of your game instead of the template)

Don't take this the wrong way, even though I had a lot of critique, this is not a bad game. I had fun playing it and hope you continue trying different concepts and working on more in the future. It's a good start, and I'm excited to see what's to come.