I need something sweetening.. what can I use?

I have a load of studies and so I've made myself a big thing of coffee, but sadly I can't drink plain coffee so I put loads of milk in it but it still tastes like plain coffee, I already looked for sugar and sweetener but my brother took the sweetener to work with him so we have none. We do have marshmallows, is there a way to like turn them into a liquid sugar for my coffee? If not is there something else I might be able to use?