Kaytee brand Fiesta Mix
Sun Seed brand Vita Rat/Mouse formula
I think I am safe to assume that all rats love food. Usually, it probably isn't the staple food that they should eat, but the human food and delicious treats that they live for.
Food
I have heard that the lab blocks (Harlan Teklad) are the best at providing a rat's nutritional needs, but I have not used it yet. There are several brands of rat food on the market, including Nutriphase Rat and Mouse Food, Kaytee Fiesta rat food, Kaytee Fortidiet Rat/Mouse food. I have read that chocolate is safe for rats on some sites, and then on others saying rats can't digest it so it's not safe. But, there are more sites that say chocolate is just fine for rats, but use sparingly as a treat. There are many things rats can eat, and will readily take. Fresh or frozen fruits and vegetables, boiled eggs, cooked meat (cooked as in just boiled with no seasoning), chicken bones, cheese, shelled nuts, uncooked/cooked pasta, oats, dry cereal (rice krispies, cheerios), dry beans, yogurt, bread, raisins. Rats can eat about the same stuff as humans, although they most often shouldn't. Be watchful on the amount of fat, sugar, and protein your rats get. Also, don't give your rats too much fruit and veggies at once. They may get diarrhea. If that happens, slowly introduce small amounts of fruit/veggies back into their diet. If you like, you can use a food bowl, but make sure it is large and heavy enough so that the rats don't tip it over. But the food might end up all over the cage anyway, so really it doesn't matter if you have a bowl or not. Try not to overfeed your rats - don't put more food in their bowl until it's nearly empty. This ensures your rat will at least eat most of the food, and not waste it.
I have found that Wal-Mart doesn't carry any rat food (I'm not sure about ALL of them, but at least the one here doesn't). I'm not sure if hamster food is adequate, but in my research I don't think that it meets the nutritional needs of a rat. Petsmart has a fairly good selection, and might be the best prices. Pet stores will most likely have higher priced items. I checked out Petco, and their prices aren't too bad, but then you have to think about shipping. For 1-51 pounds, it's $4.99 plus 20 cents a pound.
Water
Always provide plenty of fresh, clean water. A bowl may be used, but needs to be cleaned frequently, as the rats might tip it over, or dirty the water with bedding. A bottle that hangs on the side of the cage is the best option.
Treats!
Rats love treats; they live for them. And not to worry, because there are many varieties. Many of the foods listed above could be used as treats. Besides food in their staple diet, I'd say most could all be treats. You can of course buy specially made rat treats in stores, including the ones pictured below. Use treats for rewarding or encouraging your rat with good behavior, add some to their food for something else (because the same food everyday can be a little boring, right?), or give them a treat just cuz they're cute! Well, on that last one, we could go a little overboard. I don't know about all rats, but I know my rats love live mealworms.
Never feed your rats alcohol, it's a poison to them, as it is for humans. Also, do not feed your rats carbonated drinks. Rats cannot burp, and thus build up carbon dioxide in their lil tummies, which could be fatal. No spicy foods either.
