How about an apple with a light mozarella (string-) cheese stick? Or grapes with cheese? They both have some sugar, but it's from fruit. Can't go wrong with a small serving of fruit and protein! Also a serving size of trail mix (mixed nuts and dried fruit like cherries, cranberries or raisins) would be perfect. You can buy a bigger bag of trail mix and snack-size ziplock bags to prepare perfect portions to take along.