They can if they want to. They are equal to any other citizen after all. Unless there is some evidence of tampering with the results to advantage any given party.
A Cllr may wish to participate / buy tickets / enter a draw to support a fundraising event
There is ALWAYS the suggestion at such events that it is a fix. A wise Cllr might choose to resubmit the prize for another draw but so long as, in all other regards the competition is fair, the draw is the draw