I don't think you need to worry about bringing anything unless there is something very spanish you will miss.... but even that you may be able to find.
Singapore is very cosmopolitan. It has plenty of sunscreen. It probably has all of the global brands your used to.
You might try taking a look at http://www.redmart.com.sg
if you want to look for anything specific. But even if they don't have it there are a ton of speciality shops for things like cheese, wine etc.
Amazon also delivers here along with many other global e-commerce players and lots of regional players.
I would worry about bringing things of value that would be expensive to replace rather then FMCG you worry may not be available here.