it's the artificial sweetner in many diabetic foods which gives you the runs, and although these foods don't contain sugar, they may contain the same amount of carbohydrate as 'normal' foods. it's the carbohydrate (in these or any foods) which your body turns into sugar and needs to be avoided, or eaten in moderation.
the same with alcohol, drink in moderation. it has been said that a diabetic diet is not a 'special' one, it's a healthy one which we should all follow, and i think that's true,
you need to read food lables to see what 'hidden' things are in the foods you buy (glucose, fructose, lactose,etc. - another name for sugar) and avoid them.
sounds complicated and time consuming now, but in a few months you'll have got your head around it and it will have become second nature. good luck.