It depends completely on the campaign, make sure to read the description carefully and if anything, post a question in the thread. Some give out the reward in eth, btc (very few), and others reward with their own coin (which are in most cases erc20 tokens)--though you can't do anything with these tokens until they are listed on an exchange, mind you. Also, many times you won't get rewarded immediately after...
Our 'Guide to ICO's' blog post goes more into detail on this if you'd like to check it out:
http://bit.ly/ICOGuideCheers!
