There are many potential causes of passing out. As you have already noted in your question, becoming dehydrated or overheated is one of the most common causes. However, you note that it was not particularly hot at the softball game, so presumable that was not the cause.
Another common cause is pooling of blood in the legs. This commonly occurs when people are tired and standing for long periods of time, or when they are sitting and abruptly change positions. It can be relieved by flexing the legs while standing and by changing positions slowly, as well as by staying well hydrated.
If you have more episodes of dizziness or fainting
, or if you have any other concerning symptoms, such as chest pain, shortness of breath, weakness, visual changes, headache
, or palpitations, you will need to be examined by your primary care doctor
. Although serious causes of fainting in otherwise healthy people are fairly uncommon, these are symptoms that suggest there may be a more serious cause. Your doctor will be able to perform a complete physical examination and may also want to do additional diagnostic testing to rule out these more serious problems.
Good luck, and please discuss this with your doctor for more specific information!