Fine tuning a model to be a shop assistant

Prompting
1

Hi, I have an online shop that sell drinks. How can I train a custom model so it knows what we sell?
Like when a customer asks What coffee do we have?, it would respond Espresso, Americano, Latte and not Vietnamese coffee because we don’t sell that.
I have more than 100 drinks so using chat message role system like this isn’t a choice:

		openai.ChatCompletionRequest{
			Model: openai.GPT3Dot5Turbo,
			Messages: []openai.ChatCompletionMessage{
				{
					Role: openai.ChatMessageRoleSystem,
					Content: "You are a drink shop chatbot that serve these products: Hot Espresso, Cold Espresso, " +
						"Hot Latte, Cold Latte, Cold Americano, Hot Americano, Strawberry Juice, Watermelon Juice, " +
						"Lemonade Juice. Keep talking to user until you know what product they want. " +
						"Return ONLY product name without any other text when you find out."},
				{
					Role:    openai.ChatMessageRoleUser,
					Content: userMessage,
				},
			},
			User:      user,
			MaxTokens: 60,
		}