One of my favorite cheap restaurants in Abu Dhabi is Opal, in the port. Open 24 hours a day, Opal serves everything from karak and snacks to full meals. I often find myself going for lunch and for late night snacks.

For lunch, I generally get thali. I wouldn't say that Opal's thali is the best in the city, but it might be cheapest. Eight dirhams gets you unlimited stews and rice or chapati, depending on what you choose. I'm partial to the "round rice" with an added one dirham chapati. The rice goes well with the thinner, more soup like curries, and the chapati is good for eating up the delicious fried veggies. The stews are, in my mind, pretty unusual in the thali scene of Abu Dhabi. Places like Anand Al Saaed or Evergreen pretty consistently have potato stew (the bhaji that goes with puri bhaji), some sort of sweet dal, and one other legume stew (last time I went to Anand it was kidney bean, or rajma stew). All this seems pretty familiar to those familiar with the pure veg fare of Abu Dhabi. Opal's stews are generally fish or coconut based, doing away with the legume heavy curries of other spots. Perhaps my favorite coconut based dish at Opal is the diced carrots and beets fried with shaved coconut. Eating this with a piping hot chapati has become one of my greatest culinary pleasures in the city, second only to the the oily tindly at Anand.

Part of Opal's thali is a little chunk of grilled fish. This stuff is enormously flavorful, but often very bony. During the lunchtime rush after noon, they also serve a variety of other grilled fish for an additional price (a 10 inch shaari costs ~ 15 dirhams). 

Thali. Starting at the bottom left, and going clockwise: Fish stew, coconut/lentil stew, pickles, green beans and coconut, chana in a coconut gravy, and some unidentified stew that tastes like salty socks. The fish is buried under the rice under the unidentified stew. Check out that fat rice! If anyone can tell me what this rice is called I'll buy you a karak

As Opal is open 24 hours, friends and I will often end up there late at night (or early in the morning). Milky sweet karak, Chips Oman (and all its delicious variants), and the Zinker are the things to get. I wrote an article a while back about the Chips Oman sandwich. The Chips Oman sandwich is a masterpiece of junk food. The basic Chips Oman sandwich is as follows: A freshly made paratha, slathered with cream cheese spread and topped with a crunched up bag of Chips Oman chili flavored chips. Roll it up with optional but entirely necessary dakoos (hot sauce, but not Tobasco). For a long time, I was content with this three to four dirham snack. Recently, however, I've ventured into some of the other Chips Oman based creations they have at places like Opal. Adding a makanak, or hot dog, sliced length-wise and fried is pretty fantastic. The "Francisco" or a Chips Oman with bits of tandoori chicken is also darn scrumptious. Opal, and neighboring City Gate Restaurant have a whole list of Chips Oman sandwiches. I think the Opal special is eight dirhams and has a bunch of seafood on it.
Chips Oman wa makanak: Chips Oman with a hot dog.
The Francisco: Chips Oman with Tandoori Chicken. You can bet your last dirham I got some dakoos with this

Karak :)
The Zinker is a sandwich modeled off (as far as I can tell) KFC's Zinger sandwich. Usually it consists of a hot dog bun with a fried chicken, cream cheese spread, some dakoos, and some veggies. Most Zinkers that I've had have also been grilled to crisp up the trash hot dog bun.

Opal, and the port in which is resides, is a space in which men from all parts of Abu Dhabi society come to eat and shop. I say men because rarely does one see women in this part of the city. On the few occasions I've seen women at Opal or in the port, they've either stayed in their cars, or been in a mix gender group. Sitting at Opal in the evening, I've seen all sorts of men roll up to get a cup of karak and a snack: Taxi drivers, street cleaners, construction workers, men in slick, pressed kanduras and ghutrahs, men in business suits, men wearing shalwar kameez, and men in slacks and button down shirts. I've heard people speaking tons of languages from South Asia and beyond, some I can identify, others I cannot. There are few other places in the city where you can see so many different people from so many different strata of Abu Dhabi society. A sort of Arabic/English/Urdu + others pigeon language has emerged in places like the port to contend with the fact that there are people speaking so many different languages. Most of the people manning vegetable/fruit stands here can speak this pigeon.