I agree with Nateo, but I also think it's important to point out that alcohol content is related to original gravity, but they aren't identical. You could, for instance, get a really high gravity liquid by dissolving salt into the water, or gelatin. Yeast won't consume either of those compounds, though, so - although you have a very high Original Gravity - you won't get any alcohol. Only (for the most part,) fermentable sugars will be consumed by the yeast and create alcohol.
That said, not all of the compounds containing fermentable sugars are created equal. Malt will add body and flavor to a beer in addition to alcohol. Simple sugars like dextrose, sucrose, and fructose, on the other hand will not.
If all you want to do is add alcohol to your beer, I'd add a half-a-pound of dextrose. It won't affect your flavor (much). Adding a half-pound of malt to the beer, on the other hand, will make your wheat beer taste malty, and maybe even a little sour.