While no food or drink can take the place of feeding off of energy, there are some things which can help curb withdrawal symptoms and make them more tolerable until a chance to feed arises.  Specifically they help sustain your body so that your physical body puts less of a strain on you energetically.  I suggest trying each of these one at a time when you can feed, but haven't.  That way you'll know what does and doesn't work for you personally before it's an issue.

Fruit

Some people report success with fruit high in sugars (such as bananas and melons) and some report more success with sour fruit (such as lemons and limes).

Carbs

Try some healthy, unrefined carbs such as granola, rice, breads, etc.  The more whole grain the better.

Milk Products

Ice cream, cheese, and yogurt are on the top of the list.

Chocolate

Chocolate contains various chemicals which elevate mood and counters some of the affects of withdrawal.

Rare/Raw Meat

While the most obvious choice is rare or raw beef, a healthier (and much safer) option is sushi-grade fish.  Try some Sashimi; it's sushi which is just the fish.

Sports Drinks and Energy Drinks

Sports drinks are full of minerals and vitamins which can replenish that which your body is burning off faster than usual due to the need to feed.

Caffeine-filled energy drinks won't do much for most Vampires, but caffeine can cure certain kinds of headaches so if headaches are a major part of your withdrawals it might be worth a try.