Because glucose is the body’s preferred source of energy when running, it's important to eat foods that are high in carbohydrates (and that are also easy to digest) while running a half marathon.
Sports gels, chews and drinks, honey sticks, bananas, and even jelly beans are all popular, easily digestible choices for topping up your glucose supply during a half marathon 
. Raisins, chopped dates, and mini-pretzels are also good sources of energy that can be used to refuel during a long run but should be tested out before race day.
It’s important to start refueling early to keep your energy levels up, because once you bonk there’s no bouncing back. On average, both the glucose you have on board at the start of the race and your glycogen stores will be depleted after 60-90 minutes of high-intensity running (>80% VO2max) or 120 minutes of moderate-intensity running (~65% VO2max) 
, which is when bonking sets in.
You should begin refueling midway through a half marathon (around the 45-60 minute mark depending on your pace and running intensity).To maintain adequate energy levels while running a half marathon, you’ll need to consume about 30-60 g/carbohydrate/hour. Many runners prefer to split their intake into 20-minute increments to minimize GI discomfort.
Food and Fluid Guidelines Before, During, and After Exercise. (2012). Nutrition Today, 47(2), 70–71. https://doi.org/10.1097/nt.0b013e3182505bac
Bob Murray, Christine Rosenbloom, Fundamentals of glycogen metabolism for coaches and athletes, Nutrition Reviews, Volume 76, Issue 4, April 2018, Pages 243–259, https://doi.org/10.1093/nutrit/nuy001