What are your requirements for your coffee brewer and grinder? Is there any other 110 or 240 volt equipment your going to plug in to it?
Then there is the type of generator you would like to purchase. They come in gasoline, diesel, LPG, for the more portable kind. There are a few other types but my limited understanding is they are for a fixed non-moving generation.
From what little I have read up on the subject a lot of people are leaning towards diesel for the best performance for a gallon of fuel. Second place seems to go towards LPG and last for regular unleaded. LPG is considered a clean burning fuel and might actually be the best in performance since there are less EPA regulations surrounding it. Plus you don't have to worry about spilling fuel and having to pay for a clean up.