This needs the discussion of a more detailed spec:
How is the beer contained & served? Draught & glass, bottle or can? Chilled or not?
How many units of how many types of beer? Self-serve or full service?
Is a Cider option required?
Is there a hardware budget? Have you looked at available robot chassis option?
Can you weld?
Do you want to re-invent the wheel or borrow the plans?
Check this automated bartender for example that might be adapted https://www.youtube.com/watch?v=aKa0YGDu1KI