singular or plural noun used as adjective

[kohyoongliat]

Should it be 'drink stall' or 'drinks stall' ?Should it be 'vegetable stall' or 'vegetables stall' ?

[Casiopea]

In general (meaning there are exceptions) adjectives don't inflect for number. So,

a drink stall
a vegetable stall

However, given the structures here,

a stall that sells drinks
a stall that sells vegetables

you might assume, or even hear,

a drinks stall
a vegetables stall

They're non-standard. (I've heard the former, not the latter. Give it time though. )

All the best.