Cocktail, beer & coffee licencing laws.. Please Help!

There are very strict regulations, and stiff fines, for this. So you WANT to do everything correct!
You need a certification for serving alcoholic drinks (Schanklizenz) and various hygiene checks for serving food and other beverages, on top of a license for the locations where you want to place your truck and of course a proper registration of the business..
As a first step, you should contact your local company registry (Gewerbeamt) or commerce and trade agency (IHK). They can advise you which other documents or offices are required.
This is by no means doable without good German language skills, so do engage a German friend or partner! He/she should also be sufficiently frustration-tolerant, as dealing with German officialdom always involves plenty of it.

Here is a short decription on how to start a food truck business: http://de.wikihow.com/Einen-Imbisswagen-er%C3%B6ffnen
And here is information about how to get the Schanklizenz: https://www.gruenderlexikon.de/checklis … nz-kosten/