To pick a training reward for your parrot, it's not only about what food you feed them, but also when you feed it. It's really important that your parrot be hungry and want the food when you're offering it. Otherwise, it's not going to teach them or reward them for doing the behaviors that you're trying to teach them during trick training.
So, as much as it's important to pick a good treat for your parrot, it's just as important to pick a time when your parrot is hungry and wants the treats. So, a good time is generally in the morning and the evening for training sessions. In the mornings, parrots haven't had their food yet; they've been sleeping all night.
If you don't leave food in the cage at night, then the parrot will be hungry by the time you're ready to train it in the morning. So, train the parrot before you feed it its meals in the morning, while it is still hungry.
After your parrot does trick training in the morning, or is fed in the morning, you can take the food away and leave the parrot without food until the evening when you're ready to do training again.
In the evening, do your training session first while your parrot is at its hungriest. And then, after it's done training, you can give it a big meal in its cage, letting it eat as much as it wants. And then, you can take the meal away again for the night
Two meals a day are plenty for most small to large parrots. For the smaller ones, like cockatiels and budgies, you may want to feed your parrot three times a day.