Food in general has been mostly hotel meals.
Club Mahindra has a great breakfast buffet and BBQ dinner option.
For a la carte, Sterling Hotels gave a decent variety. They have a great price for the quality and quantity they served.
Alcohol is best bought from the local wine shop, Munnar has 2 such shops to what I remember. So but your drinks and chill in your hotel rooms each night and binge on room service.
There are local shops in the main Munnar town which you could walk in and eat. Sarvana Bhavan, Sangeetha, Waffle Shop, etc are the few stops to make for meals.