Depending on how much I want to take with I use different bottles. If I'm away for a few days cooking on meths then I take the trangia fuel bottle. If I only need a couple of fills I use the little bottles that the nasty energy shots things come in. They are very tough and hold enough for a couple of trangias worth.
Also if you are thinking of saving up for a trangia, you could tide yourself over with a cat food tin burner. easier to make and light than a coke can stove, if not as efficient. Tesco golden gourmet is 43p a tin. Cheaper than chips, though possibly with more horse.
