The decline in the degree of fashion for fashion apparel has caused its market value to continuously decrease, reducing market demand and creating a backlog of clothing inventory. Under these backgrounds, apparel retailers invest in experiential services to prolong the fashion level, thus to improve the demand. On the other hand, fashion apparel retailers adopt a promotional effort strategy, which is to choose an appropriate discount time point to provide a discount to consumers. We adopt a price and time dependent demand function to model the finite time horizon inventory and present a modeling framework that allows us to capture and isolate the key aspects that define a fast fashion system: Experiential services and promotional efforts. By employing this approach, we analyze four potential operating systems---traditional systems(neither provides experiential services nor discount), experiential services systems, promotional efforts systems, and fast fashion systems(with experiential services and discount). We characterize the properties of the optimal solution (the selling price, experiential services investment and discount time point) in each case. The results show that the impact of experiential services investment on marginal benefits is increased first and then decreased. The fashion apparel retailer can reduce inventory costs and increase the profitability by delaying the discounts time point. The interaction between experiential services and promotion efforts has both complementary and substitutional effects. If the deterioration rate of the fashion level of apparels is more than a critical value, the interaction of experiential services and promotional efforts has a complementarity effect, whereas the interaction of experiential services and promotional efforts has a substitutional effect when the deterioration rate is less than a critical value.