0.5 yuan. According to Weidian Food Training Website, the profit of a fried bag is 50%, and the price is one yuan. The cost price of a fried bag is in 0.5 yuan, and its expenses are mainly composed of flour, stuffing, seasoning, water and electricity, personnel expenses and so on. Water-fried buns can be used as breakfast, Chinese food, dinner and supper. Therefore, it is not a problem to sell1000-2,000 pieces a day, that is, the daily profit of water-fried buns is 1000*0.5=500 yuan.