Sig is used with 3rd person pronouns, singular and plural: hon, han, den, det and de.
Varmt kaffe och varma kläder. How do I know it's not warm coffee and hot clothes?
You don't specifically, but context and practise will prefer hot coffee and warm clothes I suppose.
"We have on us warm clothes" is the literal translation I assume. The "oss" tells us where the clothes are not who the belong to. Thanks for helping clarify.