Don’t have a full meal before. Eat some carbs (bread, pasta, etc) and not a lot of fat or protein, because those take longer to digest. Don’t eat much immediately before the tryouts.

Also, eat lunch.

1000 cal per day sounds very restrictive. Some people can’t pull that off, it sounds like you’ve done it before, so good for you if you have the discipline to do it. I’m still concerned that it may lead to binge eating or an unhealthy relationship with food in the longer term.

I’ve read that extremely restrictive diets cause the body to switch to some kind of starvation mode, which may make further weight loss more difficult. I think a less restrictive diet would be better in the long term. Maybe you can do this crash diet for a while, but I wouldn’t use it as a long term solution.