Eating old saltine crackers won't make you really sick but you can get a stomach ache and possibly vomiting and abdominal cramping from the old saltine crackers.
So it's best to not eat any old saltine crackers that smell bad such as smelling like acetone or vinegar smell to the crackers.
Old crackers that smell like vinegar or acetone could make you sick to your stomach and may cause vomiting, diarrhea etc.
You're unlikely to get food poisoning from eating the expired or old crackers but you will feel sick which has happened to me.
I once ate some crackers that smelled like vinegar and it made me sick to my stomach.
I recovered but felt really bad for awhile.
It's OK to eat expired crackers as long as the expired crackers do not smell bad.
if the expired crackers smell bad such as smelling like vinegar, acetone etc then the expired crackers should not be eaten and should be thrown out.
As crackers get old they take on a vinegar smell or a acetone smell which can make you sick to your stomach.
You're unlikely to get really sick or die from eating bad expired and old crackers that smell like vinegar or acetone but it will give you a stomach ache.
So just smell the crackers and if the expired crackers smell okay then you can eat them but if the expired crackers smell bad or taste bad then throw them out to prevent getting sick.
If the crackers are just expired for a few days to a week then they likely are okay to eat but if the crackers have been expired longer than a week or two then they are likely bad and should be thrown out.
You could thrown the old crackers outside for birds to eat or ducks.