Run your donut business, upgrade your store, create tasty donuts, keep your customers happy, watch the weather and sell sell SELL!
Keep your prices low to begin.
Try different ingredient levels, make sure you don't have too much or too little of any one ingredient. Remember, the more ingredients you have, the more your products will cost to make - so don't use too much!
If you find a good ingredient combo, then your customers will like what you sell, and your reputation will improve!
Upgrade your store and surroundings as often as you can - that will help you attract more customers and allow you to increase your prices.
The more upgrades you get, the more you can charge for things you sell.
You need a fridge to avoid milk spoilage for your coffee and milkshake products.
If an ingredient is cheap (e.g. $0.02) buy as much of it as possible to avoid high price days.
Watch the weather - on very hot days you can charge more for cold drinks and milkshakes. On cold days you can charge more for coffee and donuts.
If an item is not selling well during the day, you can adjust its price on the fly.
You can speed up the day by clicking on the fast forward button in the game interface.