I have a bottle of lime syrup, like drink syrup, and I’m thinking that it would go well with some vodka and cherry 7up. However, it’s been in the pantry for about a year now, seal broken, but capped. Can I use it?
What does it say on the ingredients list?
Does it have an expiration date?
My ExBF has a bottle (looks like a glass applesauce jar) of Dulce de Leche sent to him from his father who lived in Uruguay (American transplant) that has been in his refrigerator for the 5 years I have known him. Once in a while he takes a spoonful out and eats it…for fun (and to remember his father, who has since passed away – and not from eating the DDL!). He’s never gotten sick from it (nor have I…yes I did it. Twice.).
BON APETIT!! LOL! 
I’d suspect that if it’s sugary enough, it shouldn’t go bad, because the osmotic pressure will be whacked enough to prevent anything from growing. If it’s not sugary enough to prevent growth, then the stuff growing in it will either make it look moldy, or make it smell cidery or alcoholy, both of which are easy enough to check.
Disclaimer: I am not a doctor. Or a food scientist. Don’t trust anything you read on the internet. I take no responsibility for anything. Professional driver on closed road. Don’t try this at home.
In general very thick sugary syrups are arelatively low-moisture, and don’t support the growth of microorganisms. Even though sugar is the prime source of nutrition for many bacteria and other nasties, the lack of water inhibits their growth.
Only numbers on it are: “020043”… I assume that’s a lot number, Brand is “Hawaiice”. Ingredients: 'Water, high fructose corn syrup, gum arabic, artificial flavor, artificial color, glyceryl abietate, citric acid, and sodium benzoate.
Citric acid and Sodium Benzoate are preservatives, but they are rated for only about seven months. Probably OK, but could go at any time.
Hmm, I used some, haven’t died yet, but I’m probably going to throw it out after today. Anyways, made my drink, but realized that I have green apple flavored Smirnoff vodka. Not lime. Darn. It all tastes funny together.