Its not clear what you are saying.
Do you mean you want to prevent hunger by eating this snack bar or sustain it, you actually said 'sustain' it like its some masochistic ritual ?
To backtrack a bit, GI as you probably know is a rating system carbs pertaining to their effect on blood sugar levels. Carbs you could call 'fast transit' like liquid glucose or similar have the highest glycemic indices.
The blood sugar level goes up quickly. In response to this is whats known as pulsatile insulin secretion which corresponds to how much the blood sugar levels have been elevated which generally relates to the GI and how many carbs you just ate.
Conversely carbs that break down more slowly like those found in vegetables will result in a slower glucose transit a lot more gradually into the blood stream, have a low glycemic index.
What effects hunger is basically the blood sugar levels, but carbs in general have appetite stimulating effects. Fats and proteins would make you feel fuller, or fats / proteins with carbs, like a peanut butter sandwhich. Even if the break was high GI the Fat should blunt the insulin response somewhat.
There are other factors though, depending on how hungry you will get, including the regulation of energy balance and neurotransmitters like neuropeptide Y, which can fluctaute with different food intake levels.
In other words eating some kind of high carb high GI bar will prob just make you as hungry as eating nothing, it doesn't sound like decent food anyway. Eat another sandwhich.