The timeshare industry is famous for giving great gifts to get people to attend a timeshare presentation. The kinds of freebies you might receive range from bikes, boxes of wine, free excursions, discounts on hotel rooms, complimentary breakfasts or meals etc. In most countries, you would not be expected to pay tax on these gifts, and should not feel that you have to buy a timeshare if you accept a free gift.
In the rare circumstance that you receive a cash incentive, whether or not you would be liable to pay tax would depend on the amount you received, which is not likely to be large enough to be taxable. However, in general a timeshare company does not commonly give cash prizes but rather makes the cash incentive redeemable against a purchase of a timeshare. If you do receive cash, you should check with the tax laws of the country, although it is very unlikely you would have to pay anything for a timeshare presentation gift.