After searching a lot all over the internet for a solution to this I made my own DIY sketch style.
This is the result (see the building layer):
To create this style I did do the following steps:
1 - Export the vector layer to excel (or just create a CSV file that you can join with the layer). Give every object a random number from 0 to 1 ( in excel =RANDBETWEEN(0;1000)/1000 )
2 - Import the csv and join it to the original layer
3 - Set the first symbol layer to a gradient fill with a dark color to a greyish semitransparent color. In the example I did use a radial fill. Then I did set the first reference points x-value to the random number assigned to the polygon and the second reference points y values to 1- the random number. This is to create the random feeling of a sketch (all strokes are different).
4 - Add a second symbol layer on top of the first one. This one you set to a shapeburst fill where the outer color is transparent white and the inner color is white. Set shading style to "Shade to a set distance" with a value that is the desired width of the "strokes". In the example I did use 0,35 mm.
5 - Enjoy. I have noticed that the strokes can be hard to see when you are working with the project (graphic bug). But when exported to a map the style is working great.
I just came up with this solution so there is certainly a lot of adjustment that can be made to make it look better.