This is the easiest method to take a 2d Sprite from games and turn it into a 3d model. No complicated 3d Modeling Programs, No days learning the computer. Very little artistic skill required. Why take 30 days to learn Blender when you can have your model in a hour?

In this tutorial I only used free software. Gimp to cut up my sprite sheet. You could also just find your sprites cut. Then MagicaVoxel https://ephtracy.github.io/ the easiest 3d Modeling program I have ever seen. While I won't show the basics of how to use the program I will show the method I use to create the 3d Model.

Pull in the Front and Back View
Pull in the Side View
Clone it to width of your front/back sprite.
Delete back layers to the matching colors.

You can see the rest of the steps in the video. But you get a much better output then just building it up from scratch.