Times New Roman is an evil font. That said, the application has 3 main features "Search for drink by drink name", "Search for drink by ingredient", and "Search for drink by tag".
The ingredient one is the most interesting. "Show me all the drinks that have vodka in them... ok, now show me all the drinks that have vodka AND triple sec in them"
From the list of search results, a user would be able to select one of them which would open what I've decided to call the 'drink power page' It shows you the drink, all of the ingredients that go in the drink, the quantities, a picture, and a tags (fruity, non-alcoholic, stiff, cherry, lime, disgusting, bestseller, etc). If a user wants to, from this screen, you can 'tag' the drink (this is very similar to how most blogs work, specifically wordpress).
So far I KNOW I'm going to need an on screen keyboard, but incorporating that into the screen as 'always' visible is proving to be a little difficult, I think it's going to be hidden and only show up when the search box has focus or something. As far as the search results are concerned, I started off with a list, but scrolling on a touch screen is not easy, especially on the hardware this is going on. I want to pick up an HP Touchsmart for it, but they are outside my price range, so the enlight resistive touch screen will have to do for now. This means the search results are going to be some sort of array of buttons, right now it's a 3x3 grid, but I'm open to change it.
Why must it have an on-screen keyboard? A waterproof keyboard under the screen would work well and free up the interface, plus typing on a touchscreen isn't appealing to most people - I rarely see people writing important documents on an iPad or an iPhone.
An excellent alternative to using a keyboard at all would be a scrolling screen similar to, say, a song list on an iPhone. It functions like a directory, with the alphabet on the side to jump to a letter, it works with swipes instead of keys, it accelerates based on how hard you swipe so long lists are manageable. Easier to do that than to have someone poking keys, trusting on their spelling. A few typos by the bartender and the customer will start to lose interest.
To do the "show me vodka drinks - now add triple sec" type of stuff, make it simple. Push a button, it becomes a filter to your search; have a button for every alcohol and mixer in stock. Then when you've checked what you want, swipe in a direction to get the search results. Wanna change the search, just swipe back in the opposite direction. Use the same scrolling concept for the directory of drinks. In fact, asking by name and asking by content can be the SAME function - do a search with no filters selected and you have the entire directory. That would simplify things a bit.
Tap on a drink name, see the drink in a photo or a drawn image with the list of ingredients on the side - plus how much it costs based on ingredients chosen. Tap an ingredient to make a pop-up list for choosing a premium ingredient, such as Absolut instead of the well-brand vodka. Tap a quantity of alcohol if the customer wants it lighter or heavier than the recipe calls for - first thing I learned when I went to bartending school is that the only right way to make a drink is the way the customer wants it (and is willing to pay for it), regardless of the actual recipe.
Swipe input might not be easy on the given hardware, but there's a reason why Apple was using it and everyone started imitating it. See if you can figure a workaround. Use page down/page up in a worst case scenario, but retain the directory-style alphabet jump list on the side.
I could probably come up with more ideas. Are you working with the bartenders intended to use the interface? Do the owners have specific needs they've specified?
Also bear in mind that if this is meant as a POS interface in addition to an assistant, you need to add a screen for fast, simple access to a quick ring-up screen. Most bars don't go crazy with pricing for booze brands separately - they categorize them into three price points: well, call and top shelf.
Well booze is the cheap no-name stuff in the speed well that bartenders use. Some bars do drop a call brand in there, but they tend to be more expensive bars. Most mixed drinks are made from well booze because it's cheaper and the mixers will completely mask any premium flavors you're paying for so there's no point. Call brands are the basic name brands, like Smirnoff, Bacardi, V.O., Seagram's, Jack Daniels, etc. Top shelf are the premium ingredients - and most name-brand cordials fit here as well as single-malt Scotches, premium imports - anything that costs more than the basic call brands. Then there's the beers: domestic, import and premium, with maybe a little differentiation if you have a larger selection of beers than the average bar.
You need, if this is a POS, a quickly-accessed screen for typing up a simple drink order. In addition to the listing above sold by the shot with a simple mixer, there's juice drinks (cost a little more), two-booze drinks (like Godfathers, Rusty Nails, Black and White Russians, etc.) specialty drinks (anything with more than two or three ingredients) and the make-or-break drinks (mixed drinks that "make or break" a bartender's reputation because they're almost all booze, little to no mixer - a martini, Rob Roy, Manhattan, Old Fashioned and Gimlet). More booze in those, so they cost more, but you don't charge the three-shot price for a drink like a martini that has three shots of booze total - which is why they're priced in a different category.
Got any questions, just ask...