Below are the requirements for Upgrading the Ruined Spa in the Bay.

Upgrade 1/3
Collect 1 Tourist Breakfast (Restaurant)
Collect 2 Cloth (Workshop)
Upgrade for 684,000 Piastres

Upgrade 2/3
Collect 12 Cloth (Workshop)
Collect 185 Blood Oranges (Tropical Garden)
Collect 200 Figs (Tropical Garden)
Collect 15 Tourist Dinners (Restaurant)
Collect 10 Vegetable Cocktails (Swimming Pool)
Upgrade for 1,714,000 Piastres

Upgrade 3/3
Collect 100 Figs (Tropical Garden)
Collect 15 Fruit Plates (Restaurant)
Collect 15 Fruit Smoothies (Restaurant)
Collect 30 Vegetable Cocktails (Swimming Pool)
Collect 20 VIP Breakfast Cocktails (Swimming Pool)
Upgrade for 5,300,000 Piastres
 
Note: Once you upgrade your Spa to level 1, your Hotel tourists will start asking for Face Mask at every party. Each Face Mask takes 12 hours to be made, excluding the item collection time.